Human antibodies to S. aureus Hemolysin A toxin

ABSTRACT

The present invention provides antibodies that bind to  Staphylococcus aureus  Hemolysin A toxin, and methods of use. According to certain embodiments of the invention, the antibodies are fully human antibodies that bind to Hemolysin A. The antibodies of the invention are useful for inhibiting or neutralizing Hemolysin A activity, thus providing a means of preventing or treating a Hemolysin A-related disease or disorder such as  S. aureus  infection. In some embodiments, the antibodies of the present invention are used in treating at least one symptom or complication of a  S. aureus  infection.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No. 16/575,755, filed Sep. 19, 2019, which is a division of U.S. application Ser. No. 15/860,174, filed Jan. 2, 2018, now U.S. Pat. No. 10,463,748, which claims the benefit under 35 USC § 119(e) of U.S. Provisional Patent Application No. 62/441,786, filed Jan. 3, 2017, each of which is herein incorporated by reference in its entirety.

REFERENCE TO A SEQUENCE LISTING

This application incorporates by reference the Sequence Listing submitted in computer readable form as file 10268US03-Sequence.txt, created on Jan. 27, 2021, and containing 198,402 bytes.

FIELD OF THE INVENTION

The present invention is related to human antibodies and antigen-binding fragments thereof that specifically bind to Staphylococcus aureus Hemolysin A toxin, and to therapeutic and diagnostic methods of using such antibodies and fragments.

BACKGROUND

Staphylococcus aureus is a Gram-positive, facultative aerobic bacterium that often colonizes the skin and nose of healthy individuals. The bacterium is considered an opportunistic pathogen and can cause a variety of diseases/conditions in a number of body sites. It is a leading cause of bloodstream, skin and soft tissue and respiratory infections worldwide. The frequency of healthcare and community-associated infections caused by S. aureus has been increasing and efforts to combat these infections have been hampered by the emergence of drug-resistant strains, particularly the methicillin-resistant or MRSA strains.

S. aureus expresses a number of virulence factors (both cell surface expressed and secreted) that aid in bacterial invasion and dissemination in the host. Among the secreted virulence factors are a number of toxins, the most prominent of which is the pore-forming toxin Hemolysin A. S. aureus Hemolysin A is a 33 kDa secreted monomer that oligomerizes into a heptameric structure in the membrane of host cells to form a pore leading to cell lysis, epithelial barrier disruption, inflammation, and tissue damage (Berube et al., (2013), Toxins 5:1140-1166).

Multiple mammalian cell types, including platelets, monocytes, endothelial and epithelial cells, are lysed by Hemolysin A. It has been proposed that one or more of these cell types are the physiologically relevant targets of Hemolysin A rather than red blood cells (RBCs), as human RBCs are susceptible to lysis only when exposed to high concentrations of Hemolysin A (Hildebrand et al., (1991), J. Biol. Chem. 266:17195-17200; Wilke et al., (2010), Proc. Natl. Acad. Sci. USA 107:13473-13478; Berube et al., (2013), Toxins 5:1140-1166).

Hemolysin A has been shown to play a role in pneumonia, dermonecrosis, endocarditis, and sepsis in animal models of S. aureus infection (Tkaczyk et al., (2012), Clin. Vaccine Immunol. 19:377-385, and Kennedy et al., (2010), J. Infect. Dis. 202:1050-1058). S. aureus is a leading cause of skin and soft tissue infections (Moran, et al. (2006), N. Engl. J. Med. 355:666-674)), often causing cellulitis and skin abscesses. In mouse models, active immunization with a non-toxigenic form of Hemolysin A or passive immunization with Hemolysin A-specific antisera or monoclonal antibodies (mAbs) significantly reduces the size of skin lesions and prevents dermonecrosis caused by Hemolysin A-producing S. aureus strains (Kennedy et al., (2010), J. Infect. Dis. 202:1050-1058; Tkaczyk et al., (2012), Clin. Vaccine Immunol. 19:377-385). S. aureus is also a leading cause of pneumonia in hospitalized patients (Kollef et al., (2005), Chest 128:3854-3862 (Erratum in Chest 129:831); Shorr et al., (2006), Crit. Care 10:R97) and has been shown to play a role in mouse models of lung infection (Bubeck Wardenberg et al., (2007), Infect. Immun. 75:1040-1044). Active immunization with a non-toxigenic form of Hemolysin A or passive immunization with Hemolysin A-specific antisera or mAbs significantly reduces morbidity and mortality in mouse models of pneumonia (Bubeck Wardenburg and Schneewind, (2008), J. Exp. Med. 205:287-294; Hua et al., (2014), Antimicrob. Agents Chemother. 58:1108-1117).

Staphylococcus aureus is a leading cause of infection in hospitals and in the community. The emergence of antibiotic-resistant strains of S. aureus such as methicillin-resistant Staphylococcus aureus (MRSA), which are more difficult to treat with standard types of antibiotics, is a current problem in clinical medicine and necessitates the development of new approaches to antibacterial prophylaxis and therapy (Kennedy et al., (2010), J. Infect. Dis. 202:1050-1058).

SUMMARY OF THE INVENTION

The invention provides fully human monoclonal antibodies (mAbs) and antigen-binding fragments thereof that bind specifically to Staphylococcus aureus Hemolysin A. Such antibodies may be useful to neutralize the activity of Hemolysin A. The antibodies may act to prevent, halt the progression, or to lessen the severity of a S. aureus infections, or reduce the number, the duration, or the severity of infection recurrence, or ameliorate at least one symptom associated with infections. In some cases, the antibodies may be used to prevent or treat a condition or indication associated with S. aureus infection such as dermonecrosis, skin and soft-tissue infections (including abscesses), surgical site infections, prosthetic joint infections, bacteremia, septicemia, septic arthritis, meningitis, osteomyelitis, endocarditis, pneumonia, toxic shock syndrome, mastitis, and furunculosis and carbunculosis (boils). Such antibodies may be used alone or in conjunction with a second agent useful for treating S. aureus infections. In certain embodiments, the antibodies specific for Hemolysin A may be given therapeutically in conjunction with a second agent to lessen the severity of the S. aureus infection, or to reduce the number, the duration, or the severity of infection recurrence, or ameliorate at least one symptom associated with the S. aureus infection. In some cases, the combination therapy can be used to treat a condition or indication associated with S. aureus infection such as dermonecrosis, skin and soft-tissue infections (including abscesses), surgical site infections, prosthetic joint infections, bacteremia, septicemia, septic arthritis, meningitis, osteomyelitis, endocarditis, pneumonia, toxic shock syndrome, mastitis, and furunculosis and carbunculosis (boils). In certain embodiments, the antibodies may be used prophylactically as stand-alone therapy to protect patients who are at risk for developing a S. aureus infection. For example, certain patient populations may be at risk for developing a S. aureus infection, including elderly patients, patients who have weakened immune systems, or patients who are at a greater risk of nosocomial infection such as post-operative patients. Any of these patient populations may benefit from treatment with the antibodies of the invention, when given alone or in conjunction with a second agent.

The antibodies of the present invention may be used to treat Staphylococcus aureus infection in a patient. The antibodies can be full-length (for example, an IgG1 or IgG4 antibody) or may comprise only an antigen-binding portion (for example, a Fab, F(ab′)₂ or scFv fragment), and may be modified to affect functionality, e.g., to eliminate residual effector functions (Reddy et al., (2000), J. Immunol. 164:1925-1933) or increase mAb half-life (Zalevsky et al., (2010), Nature Biotechnology 28:157-159). The present invention includes any antibody or antigen-binding fragment thereof which comprises any of the V_(H) regions specified herein linked to a heavy chain constant region (e.g., human constant region) such as gamma (e.g., gamma-1, gamma-2, gamma-3 or gamma-4), delta, alpha, mu or epsilon and/or any V_(L) region specified herein linked to a light chain constant region (e.g., human constant region) such as lambda or kappa.

Accordingly, in a first aspect, the invention provides an isolated fully human monoclonal antibody or antigen-binding fragment thereof that specifically binds to Hemolysin A.

In some cases, the human monoclonal antibody binds to wild type Hemolysin A (SEQ ID NO: 291) or a modified Hemolysin A (SEQ ID NO: 295).

In one embodiment, the isolated human antibody or antigen-binding fragment thereof binds to Hemolysin A with a K_(D) equal to or less than 10⁻⁷ M as measured by surface plasmon resonance.

In some embodiments, the isolated antibody or antigen-binding fragment thereof exhibits one or more properties selected from the group consisting of: (a) binds to wild type Hemolysin A at 37° C. with a binding dissociation equilibrium constant (K_(D)) of less than about 80 nM as measured by surface plasmon resonance; (b) binds to wild type Hemolysin A at 37° C. with a dissociative half-life (t½) of greater than about 0.5 minutes as measured by surface plasmon resonance; (c) binds to wild type Hemolysin A at 25° C. with a K_(D) of less than about 30 nM as measured by surface plasmon resonance; (d) binds to wild type Hemolysin A at 25° C. with a t½ of greater than about 1.5 minutes as measured by surface plasmon resonance; (e) binds to a modified hemolysin A at 37° C. with a binding dissociation equilibrium constant (K_(D)) of less than about 20 nM as measured by surface plasmon resonance; (f) binds to a modified Hemolysin A at 37° C. with a dissociative half-life (t½) of greater than about 0.5 minutes as measured by surface plasmon resonance; (g) binds to a modified Hemolysin A at 25° C. with a K_(D) of less than about 10 nM as measured by surface plasmon resonance; and (11) binds to a modified hemolysin A at 25° C. with a t½ of greater than about 1.5 minutes as measured by surface plasmon resonance.

In some cases, the isolated human antibody or antigen-binding fragment thereof which binds to Hemolysin A comprises three heavy chain complementarity determining regions (CDRs) (HCDR1, HCDR2 and HCDR3) contained within any one of the heavy chain variable region (HCVR) sequences selected from the group consisting of SEQ ID NOs: 2, 22, 42, 62, 82, 102, 122, 142, 162, 182, 202, 222, 242, 262, and 282; and/or three light chain CDRs (LCDR1, LCDR2 and LCDR3) contained within any one of the light chain variable region (LCVR) sequences selected from the group consisting of SEQ ID NOs: 10, 30, 50, 70, 90, 110, 130, 150, 170, 190, 210, 230, 250, and 270. Methods and techniques for identifying CDRs within HCVR and LCVR amino acid sequences are well known in the art and can be used to identify CDRs within the specified heavy chain variable region(s) (HCVR) and/or light chain variable region(s) (LCVR) amino acid sequences disclosed herein. Exemplary conventions that can be used to identify the boundaries of CDRs include, e.g., the Kabat definition, the Chothia definition, and the AbM definition. In general terms, the Kabat definition is based on sequence variability, the Chothia definition is based on the location of the structural loop regions, and the AbM definition is a compromise between the Kabat and Chothia approaches. See, e.g., Kabat, “Sequences of Proteins of Immunological Interest,” National Institutes of Health, Bethesda, Md. (1991); Al-Lazikani et al., (1997), J. Mol. Biol. 273:927-948; and Martin et al., (1989), Proc. Natl. Acad. Sci. USA 86:9268-9272. Public databases are also available for identifying CDR sequences within an antibody.

In some embodiments, the isolated human antibody or antigen-binding fragment thereof, which binds to Hemolysin A, comprises a HCVR having an amino acid sequence selected from the group consisting of SEQ ID NOs: 2, 22, 42, 62, 82, 102, 122, 142, 162, 182, 202, 222, 242, 262, and 282.

In some embodiments, the isolated human antibody or antigen-binding fragment thereof, which binds to Hemolysin A, comprises a LCVR having an amino acid sequence selected from the group consisting of SEQ ID NOs: 10, 30, 50, 70, 90, 110, 130, 150, 170, 190, 210, 230, 250, and 270.

In some cases, the isolated human antibody or antigen-binding fragment thereof, which binds to Hemolysin A, comprises (a) a HCVR having an amino acid sequence selected from the group consisting of SEQ ID NOs: 2, 22, 42, 62, 82, 102, 122, 142, 162, 182, 202, 222, 242, 262, and 282; and (b) a LCVR having an amino acid sequence selected from the group consisting of SEQ ID NO: 10, 30, 50, 70, 90, 110, 130, 150, 170, 190, 210, 230, 250, and 270.

In one embodiment, the isolated human antibody or antigen-binding fragment thereof, which binds to Hemolysin A, comprises:

-   (a) a HCDR1 domain having an amino acid sequence selected from the     group consisting of SEQ ID NOs: 4, 24, 44, 64, 84, 104, 124, 144,     164, 184, 204, 224, 244, 264, and 284; -   (b) a HCDR2 domain having an amino acid sequence selected from the     group consisting of SEQ ID NOs: 6, 26, 46, 66, 86, 106, 126, 146,     166, 186, 206, 226, 246, 266, and 286; -   (c) a HCDR3 domain having an amino acid sequence selected from the     group consisting of SEQ ID NOs: 8, 28, 48, 68, 88, 108, 128, 148,     168, 188, 208, 228, 248, 268, and 288; -   (d) a LCDR1 domain having an amino acid sequence selected from the     group consisting of SEQ ID NOs: 12, 32, 52, 72, 92, 112, 132, 152,     172, 192, 212, 232, 252, and 272; -   (e) a LCDR2 domain having an amino acid sequence selected from the     group consisting of SEQ ID NOs: 14, 34, 54, 74, 94, 114, 134, 154,     174, 194, 214, 234, 254, and 274; and -   (f) a LCDR3 domain having an amino acid sequence selected from the     group consisting of SEQ ID NOs: 16, 36, 56, 76, 96, 116, 136, 156,     176, 196, 216, 236, 256, and 276.

In various embodiments, the invention provides a fully human monoclonal antibody or antigen-binding fragment thereof that binds to Hemolysin A, wherein the antibody or fragment thereof exhibits one or more of the following characteristics: (i) comprises a HCVR having an amino acid sequence selected from the group consisting of SEQ ID NO: 2, 22, 42, 62, 82, 102, 122, 142, 162, 182, 202, 222, 242, 262, and 282, or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity; (ii) comprises a LCVR having an amino acid sequence selected from the group consisting of SEQ ID NO: 10, 30, 50, 70, 90, 110, 130, 150, 170, 190, 210, 230, 250, and 270, or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity; (iii) comprises a HCDR3 domain having an amino acid sequence selected from the group consisting of SEQ ID NO: 8, 28, 48, 68, 88, 108, 128, 148, 168, 188, 208, 228, 248, 268, and 288, 536, 552, 568, and 584, or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity; and a LCDR3 domain having an amino acid sequence selected from the group consisting of SEQ ID NO: 16, 36, 56, 76, 96, 116, 136, 156, 176, 196, 216, 236, 256, and 276, or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity; (iv) comprises a HCDR1 domain having an amino acid sequence selected from the group consisting of SEQ ID NO: 4, 24, 44, 64, 84, 104, 124, 144, 164, 184, 204, 224, 244, 264, and 284, or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity; a HCDR2 domain having an amino acid sequence selected from the group consisting of SEQ ID NO: 6, 26, 46, 66, 86, 106, 126, 146, 166, 186, 206, 226, 246, 266, and 286, or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity; a LCDR1 domain having an amino acid sequence selected from the group consisting of SEQ ID NO: 12, 32, 52, 72, 92, 112, 132, 152, 172, 192, 212, 232, 252, and 272, or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity; and a LCDR2 domain having an amino acid sequence selected from the group consisting of SEQ ID NO: 14, 34, 54, 74, 94, 114, 134, 154, 174, 194, 214, 234, 254, and 274, or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity; and/or (v) binds to Hemolysin A with a K_(D) equal to or less than 10⁻⁷ M as measured by surface plasmon resonance.

In another aspect, the invention provides an isolated antibody or antigen-binding fragment thereof that competes for binding to Hemolysin A with a reference antibody or antigen-binding fragment comprising the complementarity determining regions (CDRs) of a heavy chain variable region (HCVR) comprising the amino acid sequence selected from the group consisting of SEQ ID NOs: 2, 22, 42, 62, 82, 102, 122, 142, 162, 182, 202, 222, 242, 262, and 282; and the CDRs of a light chain variable region (LCVR) comprising the amino acid sequence selected from the group consisting of SEQ ID NOs: 10, 30, 50, 70, 90, 110, 130, 150, 170, 190, 210, 230, 250, and 270.

In another aspect, the invention provides an isolated antibody or antigen-binding fragment thereof that binds the same epitope on Hemolysin A as a reference antibody or antigen-binding fragment comprising the CDRs of a heavy chain variable region (HCVR) comprising the amino acid sequence selected from the group consisting of SEQ ID NOs: 2, 22, 42, 62, 82, 102, 122, 142, 162, 182, 202, 222, 242, 262, and 282; and the CDRs of a light chain variable region (LCVR) comprising the amino acid sequence selected from the group consisting of SEQ ID NOs: 10, 30, 50, 70, 90, 110, 130, 150, 170, 190, 210, 230, 250, and 270.

In some embodiments, the invention provides an isolated human antibody or antigen-binding fragment thereof that binds Hemolysin A, wherein the antibody or fragment thereof comprises a HCVR/LCVR amino acid sequence pair selected from the group consisting of SEQ ID NOs: 2/10, 22/30, 42/50, 62/70, 82/90, 102/110, 122/130, 142/150, 162/170, 182/190, 202/210, 222/230, 242/250, 262/270, and 282/270.

In another aspect, the invention provides nucleic acid molecules encoding anti-Hemolysin A antibodies or fragments thereof. Recombinant expression vectors carrying the nucleic acids of the invention, and host cells into which such vectors have been introduced, are also encompassed by the invention, as are methods of producing the antibodies by culturing the host cells under conditions permitting production of the antibodies, and recovering the antibodies produced.

In some embodiments, the invention provides an antibody or fragment thereof comprising a HCVR encoded by a nucleic acid sequence selected from the group consisting of SEQ ID NO: 1, 21, 41, 61, 81, 101, 121, 141, 161, 181, 201, 221, 241, 261, and 281, or a substantially identical sequence having at least 90%, at least 95%, at least 98%, or at least 99% homology thereof.

In some embodiments, the antibody or fragment thereof further comprises a LCVR encoded by a nucleic acid sequence selected from the group consisting of SEQ ID NO: 9, 29, 49, 69, 89, 109, 129, 149, 169, 189, 209, 229, 249, and 269, or a substantially identical sequence having at least 90%, at least 95%, at least 98%, or at least 99% homology thereof.

In some cases, the invention provides an antibody or antigen-binding fragment of an antibody comprising a HCDR3 domain encoded by a nucleotide sequence selected from the group consisting of SEQ ID NO: 7, 27, 47, 67, 87, 107, 127, 147, 167, 187, 207, 227, 247, 267, and 287, or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity; and a LCDR3 domain encoded by a nucleotide sequence selected from the group consisting of SEQ ID NO: 15, 35, 55, 75, 95, 115, 135, 155, 175, 195, 215, 235, 255, and 275, or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity.

In some embodiments, the invention provides an antibody or fragment thereof further comprising a HCDR1 domain encoded by a nucleotide sequence selected from the group consisting of SEQ ID NO: 3, 23, 43, 63, 83, 103, 123, 143, 163, 183, 203, 223, 243, 263, and 283, 563, and 579, or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity; a HCDR2 domain encoded by a nucleotide sequence selected from the group consisting of SEQ ID NO: 5, 25, 45, 65, 85, 105, 125, 145, 165, 185, 205, 225, 245, 265, and 285, or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity; a LCDR1 domain encoded by a nucleotide sequence selected from the group consisting of SEQ ID NO: 11, 31, 51, 71, 91, 111, 131, 151, 171, 191, 211, 231, 251, and 271, or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity; and a LCDR2 domain encoded by a nucleotide sequence selected from the group consisting of SEQ ID NO: 13, 33, 53, 73, 93, 113, 133, 153, 173, 193, 213, 233, 253, and 273, or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity.

In some embodiments, the antibody or antigen-binding fragment thereof that binds to Hemolysin A, as described herein, may be linked to a detectable label such as a radionuclide label or an MRI-detectable label.

In another aspect, the invention provides a pharmaceutical composition comprising an isolated fully human monoclonal antibody or antigen-binding fragment thereof that binds to Hemolysin A, as described above or herein, and a pharmaceutically acceptable carrier or diluent.

In some embodiments, the pharmaceutical composition comprises a fully human monoclonal antibody that binds to Hemolysin A having any one or more of the characteristics described above or herein. In one embodiment, the antibody binds to Hemolysin A with a K_(D) equal to or less than 10⁻⁷ M. In various embodiments, the composition comprises an antibody that binds to Hemolysin A and has a HCVR/LCVR amino acid sequence pair selected from the group consisting of SEQ ID NOs: 2/10, 22/30, 42/50, 62/70, 82/90, 102/110, 122/130, 142/150, 162/170, 182/190, 202/210, 222/230, 242/250, 262/270, and 282/270. The present invention also provides an isolated human antibody or antigen-binding fragment, wherein the antibody or antigen-binding fragment comprises (i) a light chain immunoglobulin comprising the amino acid sequence set forth in SEQ ID NO: 20, and a heavy chain immunoglobulin comprising the amino acid sequence set forth in SEQ ID NO: 18; (ii) a light chain immunoglobulin comprising the amino acid sequence set forth in SEQ ID NO: 40, and a heavy chain immunoglobulin comprising the amino acid sequence set forth in SEQ ID NO: 38; (iii) a light chain immunoglobulin comprising the amino acid sequence set forth in SEQ ID NO: 60, and a heavy chain immunoglobulin comprising the amino acid sequence set forth in SEQ ID NO: 58; (iv) a light chain immunoglobulin comprising the amino acid sequence set forth in SEQ ID NO: 80, and a heavy chain immunoglobulin comprising the amino acid sequence set forth in SEQ ID NO: 78; (v) a light chain immunoglobulin comprising the amino acid sequence set forth in SEQ ID NO: 100, and a heavy chain immunoglobulin comprising the amino acid sequence set forth in SEQ ID NO: 98; (vi) a light chain immunoglobulin comprising the amino acid sequence set forth in SEQ ID NO: 120, and a heavy chain immunoglobulin comprising the amino acid sequence set forth in SEQ ID NO: 118; (vii) a light chain immunoglobulin comprising the amino acid sequence set forth in SEQ ID NO: 140, and a heavy chain immunoglobulin comprising the amino acid sequence set forth in SEQ ID NO: 138; (viii) a light chain immunoglobulin comprising the amino acid sequence set forth in SEQ ID NO: 160, and a heavy chain immunoglobulin comprising the amino acid sequence set forth in SEQ ID NO: 158; (ix) a light chain immunoglobulin comprising the amino acid sequence set forth in SEQ ID NO: 180, and a heavy chain immunoglobulin comprising the amino acid sequence set forth in SEQ ID NO: 178; (x) a light chain immunoglobulin comprising the amino acid sequence set forth in SEQ ID NO: 200, and a heavy chain immunoglobulin comprising the amino acid sequence set forth in SEQ ID NO: 198; (xi) a light chain immunoglobulin comprising the amino acid sequence set forth in SEQ ID NO: 220, and a heavy chain immunoglobulin comprising the amino acid sequence set forth in SEQ ID NO: 218; (xii) a light chain immunoglobulin comprising the amino acid sequence set forth in SEQ ID NO: 240, and a heavy chain immunoglobulin comprising the amino acid sequence set forth in SEQ ID NO: 238; (xiii) a light chain immunoglobulin comprising the amino acid sequence set forth in SEQ ID NO: 260, and a heavy chain immunoglobulin comprising the amino acid sequence set forth in SEQ ID NO: 258; (xiv) a light chain immunoglobulin comprising the amino acid sequence set forth in SEQ ID NO: 280, and a heavy chain immunoglobulin comprising the amino acid sequence set forth in SEQ ID NO: 278; or (xv) a light chain immunoglobulin comprising the amino acid sequence set forth in SEQ ID NO: 280, and a heavy chain immunoglobulin comprising the amino acid sequence set forth in SEQ ID NO: 290.

In some cases, the invention features a composition, which is a combination of an antibody or antigen-binding fragment of an antibody of the invention, and a second therapeutic agent. The second therapeutic agent may be a small molecule drug, a protein/polypeptide, an antibody, a nucleic acid molecule, such as an anti-sense oligonucleotide, or a siRNA. The second therapeutic agent may be synthetic or naturally derived. The second therapeutic agent may be any agent that is advantageously combined with the antibody or fragment thereof of the invention.

In certain embodiments, the second therapeutic agent may be an agent that helps to counteract or reduce any possible side effect(s) associated with the antibody or antigen-binding fragment of an antibody of the invention, if such side effect(s) should occur.

It will also be appreciated that the antibodies and pharmaceutically acceptable compositions of the present invention can be employed in combination therapies, that is, the antibodies and pharmaceutically acceptable compositions can be administered concurrently with, prior to, or subsequent to, one or more other desired therapeutics or medical procedures. The particular combination of therapies (therapeutics or procedures) to employ in a combination regimen will take into account compatibility of the desired therapeutics and/or procedures and the desired therapeutic effect to be achieved. It will also be appreciated that the therapies employed may achieve a desired effect for the same disorder (for example, an antibody may be administered concurrently with another agent used to treat the same disorder), or they may achieve different effects (e.g., control of any adverse effects). As used herein, additional therapeutic agents that are normally administered to treat or prevent a particular disease, or condition, are appropriate for the disease, or condition, being treated. When multiple therapeutics are co-administered, dosages may be adjusted accordingly, as is recognized in the pertinent art.

In another aspect, the invention provides a method for preventing, treating or managing primary infections caused by Staphylococcus aureus, and reducing, eliminating or preventing relapse from S. aureus infections. In some cases, the invention includes a method for preventing and/or treating a disease or disorder associated with S. aureus infection, such as dermonecrosis, skin and soft-tissue infections (including abscesses), surgical site infections, prosthetic joint infections, bacteremia, septicemia, septic arthritis, meningitis, osteomyelitis, endocarditis, pneumonia, toxic shock syndrome, mastitis, and furunculosis and carbunculosis (boils). In certain embodiments, the invention provides a method for treating a patient suffering from S. aureus infection, or for treating at least one symptom or complication associated with S. aureus infection, or halting the progression of S. aureus infection, the method comprising administering to the patient an effective amount of an antibody or an antigen-binding fragment thereof that binds to Hemolysin A; or a pharmaceutical composition comprising an effective amount of an antibody or an antigen-binding fragment thereof that binds to Hemolysin A, such that the Staphylococcus aureus infection-associated condition or disease is either prevented, or lessened in severity and/or duration, or at least one symptom or complication associated with the condition or disease is prevented, or ameliorated, or that the frequency and/or duration of, or the severity of S. aureus infection is reduced. In various embodiments of the methods discussed above, the S. aureus bacteria may be resistant to one or more types of antibiotic treatments. In one embodiment, the bacteria are methicillin-resistant S. aureus (MRSA).

In some embodiments of the method, the pharmaceutical composition comprising the antibodies of the invention is administered to the patient in combination with a second therapeutic agent.

In embodiments of the invention, the antibody or antigen-binding fragment thereof or the pharmaceutical composition comprising the antibody is administered subcutaneously, intravenously, intradermally, orally or intramuscularly.

In related embodiments, the invention includes the use of an isolated anti-Hemolysin A antibody or antigen binding portion of an antibody of the invention in the manufacture of a medicament for the prevention or treatment of a disease or disorder related to or caused by S. aureus infection or the presence of Hemolysin A toxin. The invention also includes use of an isolated anti-Hemolysin A antibody or antigen binding portion thereof for preventing or treating a disease or disorder related to or caused by S. aureus infection or the presence of Hemolysin A toxin. In various embodiments, these diseases or disorders include dermonecrosis, skin and soft-tissue infections (including abscesses), surgical site infections, prosthetic joint infections, bacteremia, septicemia, septic arthritis, meningitis, osteomyelitis, endocarditis, pneumonia, toxic shock syndrome, mastitis, and furunculosis and carbunculosis (boils). In one embodiment, the invention includes the use of an isolated anti-Hemolysin A antibody or antigen-binding fragment thereof in the manufacture of a medicament for the treatment of a S. aureus infection. In some cases, the invention includes the use of an anti-Hemolysin A antibody or antigen-binding fragment thereof as discussed above or herein for treating a patient suffering from or at risk of developing a Staphylococcus aureus infection. In some embodiments, the invention includes the use of an anti-Hemolysin A antibody or antigen-binding fragment thereof as discussed above or herein for treating a patient suffering from dermonecrosis, skin and soft-tissue infections (including abscesses), surgical site infections, prosthetic joint infections, bacteremia, septicemia, septic arthritis, meningitis, osteomyelitis, endocarditis, pneumonia, toxic shock syndrome, mastitis, and furunculosis and carbunculosis (boils).

Other embodiments will become apparent from a review of the ensuing detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows binding of anti-Hemolysin A antibodies to S. aureus Hemolysin A.

FIGS. 2 a, 2 b and 2 c show binding of anti-Hemolysin A antibodies to F subunits of S. aureus bicomponent toxins: FIG. 2 a shows binding to LukF; FIG. 2 b shows binding to LukD; and FIG. 2 c shows binding to HlgB.

FIGS. 3 a, 3 b and 3 c show binding of anti-Hemolysin A antibody H1H15381P to components of S. aureus bicomponent toxins: FIG. 3 a shows binding to LukF, LukS, and LukE; FIG. 3 b shows binding to HlgA and HlgC; and FIG. 3 c shows binding to delta toxin.

FIGS. 4 a and 4 b : FIG. 4 a shows blocking of toxin-induced ADAM10 activity by anti-Hemolysin A antibody H1H15377P, H1H15381P or H1H15399P and FIG. 4 b shows prevention of Hemolysin A binding to rabbit red blood cell membranes by anti-Hemolysin A antibody H1H15377 or H1H15399.

FIGS. 5 a, 5 b and 5 c show size of dermonecrotic lesions in mice infected with S.aureus CA-127 and treated with various antibodies (H1H15377P, H1H15381P, H1H15399P, LTM14, LC10 or control antibody) at 5, 0.5 or 0.125 mg/kg.

FIGS. 6 a, 6 b and 6 c show size of dermonecrotic lesions in mice infected with S.aureus Newman and treated with various antibodies (H1H15377P, H1H15381P, H1H15399P, LTM14, LC10 or control antibody) at 5, 0.5 or 0.125 mg/kg.

FIGS. 7 a and 7 b show S.aureus CA-127 (MRSA) or S.aureus Newman (MSSA) bacteria counts in skin of mice administered various anti-Hemolysin A mAbs (H1H15377P, H1H15381P, H1H15399P, LTM14, LC10 or control antibody).

FIGS. 8 a and 8 b show bacterial burden in lungs of mice infected with S.aureus CA-127 treated with various antibodies (H1H15377P, H1H15381P, H1H15399P, LTM14, LC10 or control antibody) at 1.25 or 0.325 mg/kg.

DETAILED DESCRIPTION

Before the present methods are described, it is to be understood that this invention is not limited to particular methods, and experimental conditions described, as such methods and conditions may vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting, since the scope of the present invention will be limited only by the appended claims.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, preferred methods and materials are now described. All publications mentioned herein are incorporated herein by reference in their entirety.

Definitions

The terms “Hemolysin A” and “Hemolysin A toxin” refer, interchangeably, to a 33 kDa monomeric protein secreted by S. aureus that oligomerizes into a heptameric structure in the membrane of host cells to form a pore leading to cell lysis, inflammation, and tissue damage. The amino acid sequence of wild type Hemolysin A is shown in SEQ ID NO: 291. The amino acid sequence of a modified Hemolysin A (H35L mutant) is shown in SEQ ID NO: 295. Unless otherwise noted, reference to Hemolysin A refers to the wild type form. Hla-H35L is Hemolysin A in which the histidine at position 35 has been changed to a leucine. This allows for the toxin to assemble on the host cell membrane up to the pre-pore formation step but a fully functional pore is not formed. This renders Hemolysin A non-toxigenic.

The term “antibody”, as used herein, is intended to refer to immunoglobulin molecules comprised of four polypeptide chains, two heavy (H) chains and two light (L) chains inter-connected by disulfide bonds (i.e., “full antibody molecules”), as well as multimers thereof (e.g. IgM) or antigen-binding fragments thereof. Each heavy chain is comprised of a heavy chain variable region (“HCVR” or “V_(H)”) and a heavy chain constant region (comprised of domains C_(H)1, C_(H)2 and C_(H)3). Each light chain is comprised of a light chain variable region (“LCVR or “V_(L)”) and a light chain constant region (C_(L)). The V_(H) and V_(L) regions can be further subdivided into regions of hypervariability, termed complementarity determining regions (CDR), interspersed with regions that are more conserved, termed framework regions (FR). Each V_(H) and V_(L) is composed of three CDRs and four FRs, arranged from amino-terminus to carboxy-terminus in the following order: FR1, CDR1, FR2, CDR2, FR3, CDR3, FR4. In certain embodiments of the invention, the FRs of the antibody (or antigen binding fragment thereof) may be identical to the human germline sequences, or may be naturally or artificially modified. An amino acid consensus sequence may be defined based on a side-by-side analysis of two or more CDRs.

Substitution of one or more CDR residues or omission of one or more CDRs is also possible. Antibodies have been described in the scientific literature in which one or two CDRs can be dispensed with for binding. Padlan et al. (FASEB J. 1995, 9:133-139) analyzed the contact regions between antibodies and their antigens, based on published crystal structures, and concluded that only about one fifth to one third of CDR residues actually contact the antigen. Padlan also found many antibodies in which one or two CDRs had no amino acids in contact with an antigen (see also, Vajdos et al. 2002 J Mol Biol 320:415-428).

CDR residues not contacting antigen can be identified based on previous studies (for example residues H60-H65 in CDRH2 are often not required), from regions of Kabat CDRs lying outside Chothia CDRs, by molecular modeling and/or empirically. If a CDR or residue(s) thereof is omitted, it is usually substituted with an amino acid occupying the corresponding position in another human antibody sequence or a consensus of such sequences. Positions for substitution within CDRs and amino acids to substitute can also be selected empirically. Empirical substitutions can be conservative or non-conservative substitutions.

The fully human anti-Hemolysin A monoclonal antibodies disclosed herein may comprise one or more amino acid substitutions, insertions and/or deletions in the framework and/or CDR regions of the heavy and light chain variable domains as compared to the corresponding germline sequences. Such mutations can be readily ascertained by comparing the amino acid sequences disclosed herein to germline sequences available from, for example, public antibody sequence databases. The present invention includes antibodies, and antigen-binding fragments thereof, which are derived from any of the amino acid sequences disclosed herein, wherein one or more amino acids within one or more framework and/or CDR regions are mutated to the corresponding residue(s) of the germline sequence from which the antibody was derived, or to the corresponding residue(s) of another human germline sequence, or to a conservative amino acid substitution of the corresponding germline residue(s) (such sequence changes are referred to herein collectively as “germline mutations”). A person of ordinary skill in the art, starting with the heavy and light chain variable region sequences disclosed herein, can easily produce numerous antibodies and antigen-binding fragments that comprise one or more individual germline mutations or combinations thereof. In certain embodiments, all of the framework and/or CDR residues within the V_(H) and/or V_(L) domains are mutated back to the residues found in the original germline sequence from which the antibody was derived. In other embodiments, only certain residues are mutated back to the original germline sequence, e.g., only the mutated residues found within the first 8 amino acids of FR1 or within the last 8 amino acids of FR4, or only the mutated residues found within CDR1, CDR2 or CDR3. In other embodiments, one or more of the framework and/or CDR residue(s) are mutated to the corresponding residue(s) of a different germline sequence (i.e., a germline sequence that is different from the germline sequence from which the antibody was originally derived). Furthermore, the antibodies of the present invention may contain any combination of two or more germline mutations within the framework and/or CDR regions, e.g., wherein certain individual residues are mutated to the corresponding residue of a particular germline sequence while certain other residues that differ from the original germline sequence are maintained or are mutated to the corresponding residue of a different germline sequence. Once obtained, antibodies and antigen-binding fragments that contain one or more germline mutations can be easily tested for one or more desired property such as, improved binding specificity, increased binding affinity, improved or enhanced antagonistic or agonistic biological properties (as the case may be), reduced immunogenicity, etc. Antibodies and antigen-binding fragments obtained in this general manner are encompassed within the present invention.

The present invention also includes fully human anti-Hemolysin A monoclonal antibodies comprising variants of any of the HCVR, LCVR, and/or CDR amino acid sequences disclosed herein having one or more conservative substitutions. For example, the present invention includes anti-hemolysin A antibodies having HCVR, LCVR, and/or CDR amino acid sequences with, e.g., 10 or fewer, 8 or fewer, 6 or fewer, 4 or fewer, etc. conservative amino acid substitutions relative to any of the HCVR, LCVR, and/or CDR amino acid sequences disclosed herein.

The term “human antibody”, as used herein, is intended to include antibodies having variable and constant regions derived from human germline immunoglobulin sequences. The human mAbs of the invention may include amino acid residues not encoded by human germline immunoglobulin sequences (e.g., mutations introduced by random or site-specific mutagenesis in vitro or by somatic mutation in vivo), for example in the CDRs and in particular CDR3. However, the term “human antibody”, as used herein, is not intended to include mAbs in which CDR sequences derived from the germline of another mammalian species (e.g., mouse), have been grafted onto human FR sequences.

The term “specifically binds,” or “binds specifically to”, or the like, means that an antibody or antigen-binding fragment thereof forms a complex with an antigen that is relatively stable under physiologic conditions. Specific binding can be characterized by an equilibrium dissociation constant of at least about 1×10⁻⁶ M or less (e.g., a smaller K_(D) denotes a tighter binding). Methods for determining whether two molecules specifically bind are well known in the art and include, for example, equilibrium dialysis, surface plasmon resonance, and the like. As described herein, antibodies that bind specifically to Hemolysin A have been identified by surface plasmon resonance, e.g., BIACORE™. Moreover, multi-specific antibodies that bind to one domain in Hemolysin A and one or more additional antigens or a bi-specific that binds to two different regions of Hemolysin A are nonetheless considered antibodies that “specifically bind”, as used herein.

The term “high affinity” antibody refers to those mAbs having a binding affinity to Hemolysin A, expressed as K_(D), of at least 10⁻⁷ M; preferably 10⁻⁸ M; more preferably 10⁻⁹M, even more preferably 10⁻¹⁰ M, even more preferably 10⁻¹¹ M, as measured by surface plasmon resonance, e.g., BIACORE™ or solution-affinity ELISA.

By the term “slow off rate”, “Koff” or “kd” is meant to describe an antibody that dissociates from Hemolysin A with a rate constant of 1×10⁻³ s⁻¹ or less, preferably 1×10⁻⁴ s⁻¹ or less, as determined by surface plasmon resonance, e.g., BIACORE™.

The terms “antigen-binding portion” of an antibody, “antigen-binding fragment” of an antibody, and the like, as used herein, include any naturally occurring, enzymatically obtainable, synthetic, or genetically engineered polypeptide or glycoprotein that specifically binds an antigen to form a complex. The terms “antigen-binding fragment” of an antibody, or “antibody fragment”, as used herein, refers to one or more fragments of an antibody that retain the ability to bind to Hemolysin A.

In specific embodiments, antibody or antibody fragments of the invention may be conjugated to a therapeutic moiety (“immunoconjugate”), such as an antibiotic, a second anti-Hemolysin A antibody, or an antibody to a cytokine such as IL-1, IL-6, or TGF-β, or any other therapeutic moiety useful for treating a disease or condition including Staphylococcus aureus infection, skin and soft-tissue infections (including abscesses), surgical site infections, prosthetic joint infections, bacteremia, septicemia, septic arthritis, meningitis, osteomyelitis, endocarditis, pneumonia, toxic shock syndrome, mastitis, and furunculosis and carbunculosis (boils).

An “isolated antibody”, as used herein, is intended to refer to an antibody that is substantially free of other antibodies (Abs) having different antigenic specificities (e.g., an isolated antibody that specifically binds Hemolysin A, or a fragment thereof, is substantially free of Abs that specifically bind antigens other than Hemolysin A).

The term “surface plasmon resonance”, as used herein, refers to an optical phenomenon that allows for the analysis of real-time biomolecular interactions by detection of alterations in protein concentrations within a biosensor matrix, for example using the BIACORE™ system (Pharmacia Biosensor AB, Uppsala, Sweden and Piscataway, N.J.).

The term “K_(D)”, as used herein, is intended to refer to the equilibrium dissociation constant of a particular antibody-antigen interaction.

The term “epitope” refers to an antigenic determinant that interacts with a specific antigen-binding site in the variable region of an antibody molecule known as a paratope. A single antigen may have more than one epitope. Thus, different antibodies may bind to different areas on an antigen and may have different biological effects. The term “epitope” also refers to a site on an antigen to which B and/or T cells respond. It also refers to a region of an antigen that is bound by an antibody. Epitopes may be defined as structural or functional. Functional epitopes are generally a subset of the structural epitopes and have those residues that directly contribute to the affinity of the interaction. Epitopes may also be conformational, that is, composed of non-linear amino acids. In certain embodiments, epitopes may include determinants that are chemically active surface groupings of molecules such as amino acids, sugar side chains, phosphoryl groups, or sulfonyl groups, and, in certain embodiments, may have specific three-dimensional structural characteristics, and/or specific charge characteristics.

The term “substantial identity” or “substantially identical,” when referring to a nucleic acid or fragment thereof, indicates that, when optimally aligned with appropriate nucleotide insertions or deletions with another nucleic acid (or its complementary strand), there is nucleotide sequence identity in at least about 90%, and more preferably at least about 95%, 96%, 97%, 98% or 99% of the nucleotide bases, as measured by any well-known algorithm of sequence identity, such as FASTA, BLAST or GAP, as discussed below. A nucleic acid molecule having substantial identity to a reference nucleic acid molecule may, in certain instances, encode a polypeptide having the same or substantially similar amino acid sequence as the polypeptide encoded by the reference nucleic acid molecule.

As applied to polypeptides, the term “substantial similarity” or “substantially similar” means that two peptide sequences, when optimally aligned, such as by the programs GAP or BESTFIT using default gap weights, share at least 90% sequence identity, even more preferably at least 95%, 98% or 99% sequence identity. Preferably, residue positions, which are not identical, differ by conservative amino acid substitutions. A “conservative amino acid substitution” is one in which an amino acid residue is substituted by another amino acid residue having a side chain (R group) with similar chemical properties (e.g., charge or hydrophobicity). In general, a conservative amino acid substitution will not substantially change the functional properties of a protein. In cases where two or more amino acid sequences differ from each other by conservative substitutions, the percent or degree of similarity may be adjusted upwards to correct for the conservative nature of the substitution. Means for making this adjustment are well known to those of skill in the art. See, e.g., Pearson (1994) Methods Mol. Biol. 24: 307-331, which is herein incorporated by reference. Examples of groups of amino acids that have side chains with similar chemical properties include 1) aliphatic side chains: glycine, alanine, valine, leucine and isoleucine; 2) aliphatic-hydroxyl side chains: serine and threonine; 3) amide-containing side chains: asparagine and glutamine; 4) aromatic side chains: phenylalanine, tyrosine, and tryptophan; 5) basic side chains: lysine, arginine, and histidine; 6) acidic side chains: aspartate and glutamate, and 7) sulfur-containing side chains: cysteine and methionine. Preferred conservative amino acids substitution groups are: valine-leucine-isoleucine, phenylalanine-tyrosine, lysine-arginine, alanine-valine, glutamate-aspartate, and asparagine-glutamine. Alternatively, a conservative replacement is any change having a positive value in the PAM250 log-likelihood matrix disclosed in Gonnet et al. (1992) Science 256: 1443 45, herein incorporated by reference. A “moderately conservative” replacement is any change having a nonnegative value in the PAM250 log-likelihood matrix.

Sequence similarity for polypeptides is typically measured using sequence analysis software. Protein analysis software matches similar sequences using measures of similarity assigned to various substitutions, deletions and other modifications, including conservative amino acid substitutions. For instance, GCG software contains programs such as GAP and BESTFIT which can be used with default parameters to determine sequence homology or sequence identity between closely related polypeptides, such as homologous polypeptides from different species of organisms or between a wild type protein and a mutein thereof. See, e.g., GCG Version 6.1. Polypeptide sequences also can be compared using FASTA with default or recommended parameters; a program in GCG Version 6.1. FASTA (e.g., FASTA2 and FASTA3) provides alignments and percent sequence identity of the regions of the best overlap between the query and search sequences (Pearson (2000) supra). Another preferred algorithm when comparing a sequence of the invention to a database containing a large number of sequences from different organisms is the computer program BLAST, especially BLASTP or TBLASTN, using default parameters. See, e.g., Altschul et al. (1990) J. Mol. Biol. 215: 403-410 and (1997) Nucleic Acids Res. 25: 3389-3402, each of which is herein incorporated by reference.

In specific embodiments, the antibody or antibody fragment for use in the method of the invention may be mono-specific, bi-specific, or multi-specific. Multi-specific antibodies may be specific for different epitopes of one target polypeptide or may contain antigen-binding domains specific for epitopes of more than one target polypeptide. An exemplary bi-specific antibody format that can be used in the context of the present invention involves the use of a first immunoglobulin (Ig) C_(H)3 domain and a second Ig C_(H)3 domain, wherein the first and second Ig C_(H)3 domains differ from one another by at least one amino acid, and wherein at least one amino acid difference reduces binding of the bi-specific antibody to Protein A as compared to a bi-specific antibody lacking the amino acid difference. In one embodiment, the first Ig C_(H)3 domain binds Protein A and the second Ig C_(H)3 domain contains a mutation that reduces or abolishes Protein A binding such as an H95R modification (by IMGT exon numbering; H435R by EU numbering). The second C_(H)3 may further comprise an Y96F modification (by IMGT; Y436F by EU). Further modifications that may be found within the second C_(H)3 include: D16E, L18M, N44S, K52N, V57M, and V82I (by IMGT; D356E, L358M, N384S, K392N, V397M, and V422I by EU) in the case of IgG1 mAbs; N44S, K52N, and V82I (IMGT; N384S, K392N, and V422I by EU) in the case of IgG2 mAbs; and Q15R, N44S, K52N, V57M, R69K, E79Q, and V82I (by IMGT; Q355R, N384S, K392N, V397M, R409K, E419Q, and V422I by EU) in the case of IgG4 mAbs. Variations on the bi-specific antibody format described above are contemplated within the scope of the present invention.

By the phrase “therapeutically effective amount” is meant an amount that produces the desired effect for which it is administered. The exact amount will depend on the purpose of the treatment, and will be ascertainable by one skilled in the art using known techniques (see, for example, Lloyd (1999) The Art, Science and Technology of Pharmaceutical Compounding).

General Description

Staphylococcus aureus Hemolysin A toxin is a 33 kDa secreted monomeric protein that oligomerizes into a heptameric structure in the membrane of host cells to form a pore leading to cell lysis, inflammation, and tissue damage. Hemolysin A has been shown to play a role in pneumonia, dermonecrosis, endocarditis, and sepsis.

The antibodies described herein demonstrate specific binding to Hemolysin A and in some embodiments, may be useful for treating patients suffering from S. aureus infections, or preventing such infections. The use of such antibodies may be an effective means of treating patients suffering from S. aureus infection, or may be used to lessen the severity of the symptoms of a S. aureus infection. They may be used alone or as adjunct therapy with other therapeutic moieties or modalities known in the art for treating Staphylococcus aureus infection, such as, but not limited to, an antibiotic, a non-steroidal anti-inflammatory drug (NSIAD) (or other palliative therapy), or a corticosteroid such as prednisone. They may be used in conjunction with additional antibodies specific for antigens other than Hemolysin A, or may combined with other types of treatments.

In some embodiments, the antibodies described herein may be useful in preventing, treating or managing a disease or condition of Staphylococcus aureus infection including, but not limited to, dermonecrosis, skin and soft-tissue infections (including abscesses), surgical site infections, prosthetic joint infections, bacteremia, septicemia, septic arthritis, meningitis, osteomyelitis, endocarditis, pneumonia, toxic shock syndrome, mastitis, and furunculosis and carbunculosis (boils).

In certain embodiments, the antibodies of the invention are obtained from mice immunized with a primary immunogen, such as a native, full length Hemolysin A (SEQ ID NO: 291) or with a modified form of Hemolysin A (SEQ ID NO: 295) or Hemolysin A fragments, followed by immunization with a secondary immunogen, or with an immunogenically active fragment of Hemolysin A.

The immunogen may be an immunogenic fragment of Hemolysin A or DNA encoding the fragment thereof. The immunogen may be Hemolysin A coupled to a histidine tag and/or to a fragment of Fc region of an antibody.

The amino acid sequence of full length Hemolysin A is shown as SEQ ID NO: 291. The full length amino acid sequence of modified Hemolysin A is shown as SEQ ID NO: 295.

In certain embodiments, antibodies that bind specifically to Hemolysin A may be prepared using fragments of the above-noted regions, or peptides that extend beyond the designated regions by about 5 to about 20 amino acid residues from either, or both, the N or C terminal ends of the regions described herein. In certain embodiments, any combination of the above-noted regions or fragments thereof may be used in the preparation of Hemolysin A-specific antibodies. In certain embodiments, any one or more of the above-noted regions of Hemolysin A, or fragments thereof may be used for preparing monospecific, bispecific, or multispecific antibodies.

Antigen-Binding Fragments of Antibodies

Unless specifically indicated otherwise, the term “antibody,” as used herein, shall be understood to encompass antibody molecules comprising two immunoglobulin heavy chains and two immunoglobulin light chains (i.e., “full antibody molecules”) as well as antigen-binding fragments thereof. The terms “antigen-binding portion” of an antibody, “antigen-binding fragment” of an antibody, and the like, as used herein, include any naturally occurring, enzymatically obtainable, synthetic, or genetically engineered polypeptide or glycoprotein that specifically binds an antigen to form a complex. The terms “antigen-binding fragment” of an antibody, or “antibody fragment”, as used herein, refers to one or more fragments of an antibody that retain the ability to specifically bind to Hemolysin A. An antibody fragment may include a Fab fragment, a F(ab′)₂ fragment, a Fv fragment, a dAb fragment, a fragment containing a CDR, or an isolated CDR. Antigen-binding fragments of an antibody may be derived, e.g., from full antibody molecules using any suitable standard techniques such as proteolytic digestion or recombinant genetic engineering techniques involving the manipulation and expression of DNA encoding antibody variable and (optionally) constant domains. Such DNA is known and/or is readily available from, e.g., commercial sources, DNA libraries (including, e.g., phage-antibody libraries), or can be synthesized. The DNA may be sequenced and manipulated chemically or by using molecular biology techniques, for example, to arrange one or more variable and/or constant domains into a suitable configuration, or to introduce codons, create cysteine residues, modify, add or delete amino acids, etc.

Non-limiting examples of antigen-binding fragments include: (i) Fab fragments; (ii) F(ab′)2 fragments; (iii) Fd fragments; (iv) Fv fragments; (v) single-chain Fv (scFv) molecules; (vi) dAb fragments; and (vii) minimal recognition units consisting of the amino acid residues that mimic the hypervariable region of an antibody (e.g., an isolated complementarity determining region (CDR) such as a CDR3 peptide), or a constrained FR3-CDR3-FR4 peptide. Other engineered molecules, such as domain-specific antibodies, single-domain antibodies, domain-deleted antibodies, chimeric antibodies, CDR-grafted antibodies, diabodies, triabodies, tetrabodies, minibodies, nanobodies (e.g. monovalent nanobodies, bivalent nanobodies, etc.), small modular immunopharmaceuticals (SMIPs), and shark variable IgNAR domains, are also encompassed within the expression “antigen-binding fragment,” as used herein.

An antigen-binding fragment of an antibody will typically comprise at least one variable domain. The variable domain may be of any size or amino acid composition and will generally comprise at least one CDR, which is adjacent to or in frame with one or more framework sequences. In antigen-binding fragments having a V_(H) domain associated with a V_(L) domain, the V_(H) and V_(L) domains may be situated relative to one another in any suitable arrangement. For example, the variable region may be dimeric and contain V_(H)-V_(H), V_(H)-V_(L) or V_(L)-V_(L) dimers. Alternatively, the antigen-binding fragment of an antibody may contain a monomeric V_(H) or V_(L) domain.

In certain embodiments, an antigen-binding fragment of an antibody may contain at least one variable domain covalently linked to at least one constant domain. Non-limiting, exemplary configurations of variable and constant domains that may be found within an antigen-binding fragment of an antibody of the present invention include: (i) V_(H)-C_(H)1; V_(H)-C_(H)2; V_(H)-C_(H)3; (iv) V_(H)-C_(H)1-C_(H)2; (V) V_(H)-C_(H)1-C_(H)2-C_(H)3; (Vi) V_(H)-C_(H)2-C_(H)3; (Vii) V_(H)-C_(L); (viii) V_(L)-C_(H)1; (ix) V_(L)-C_(H)2; (x) V_(L)-C_(H)3; (xi) V_(L)-C_(H)1-C_(H)2; (xii) V_(L)-C_(H)1-C_(H)2-C_(H)3; (xiii) V_(L)-C_(H)2-C_(H)3; and (xiv) V_(L)-C_(L). In any configuration of variable and constant domains, including any of the exemplary configurations listed above, the variable and constant domains may be either directly linked to one another or may be linked by a full or partial hinge or linker region. A hinge region may consist of at least 2 (e.g., 5, 10, 15, 20, 40, 60 or more) amino acids, which result in a flexible or semi-flexible linkage between adjacent variable and/or constant domains in a single polypeptide molecule. Moreover, an antigen-binding fragment of an antibody of the present invention may comprise a homo-dimer or hetero-dimer (or other multimer) of any of the variable and constant domain configurations listed above in non-covalent association with one another and/or with one or more monomeric V_(H) or V_(L) domain (e.g., by disulfide bond(s)).

As with full antibody molecules, antigen-binding fragments may be mono-specific or multi-specific (e.g., bi-specific). A multi-specific antigen-binding fragment of an antibody will typically comprise at least two different variable domains, wherein each variable domain is capable of specifically binding to a separate antigen or to a different epitope on the same antigen. Any multi-specific antibody format, including the exemplary bi-specific antibody formats disclosed herein, may be adapted for use in the context of an antigen-binding fragment of an antibody of the present invention using routine techniques available in the art.

The present invention includes anti-hemolysin A antibodies and antigen-binding fragments having immunoglobulin chains that include the amino acid sequences set forth herein as well as variants having cellular and/or in vitro post-translational modifications. For example, the present invention includes antibodies and antigen-binding fragments thereof that specifically bind to hemolysin A comprising heavy and/or light chain amino acid sequences set forth herein (e.g., CDR-H1, CDR-H2, CDR-H3, CDR-L1, CDR-L2 and/or CDR-L3) as well as antibodies and fragments wherein one or more amino acid residues is glycosylated, one or more Asn residues is deamidated, one or more residues (e.g., Met, Trp and/or His) is oxidized, the N-terminal Gln is pyroglutamate (pyroE) and/or the C-terminal Lysine is missing.

The present invention includes recombinant methods for making anti-hemolysin A antibodies or antigen-binding fragments thereof of the present invention, or an immunoglobulin chain thereof, comprising (i) introducing one or more polynucleotides encoding a light and/or a heavy immunoglobulin chain of said antibody or antigen-binding fragment (e.g., a heavy chain or V_(H) thereof or immunoglobulin comprising the HCDR1, HCDR2 and HCDR3 thereof and/or a light chain or V_(L) thereof or immunoglobulin comprising the LCDR1, LCDR2 and LCDR3 thereof), for example, wherein the polynucleotide is in a vector and/or is operably linked to a promoter; (ii) culturing the host cell (e.g., Chinese hamster ovary (CHO) cell or Pichia cell or Pichia pastoris cell) under condition favorable to expression of the polynucleotide(s) and, (iii) optionally, isolating the antibody or fragment or chain from the host cell and/or medium in which the host cell is grown. When making an antibody or antigen-binding fragment comprising more than one immunoglobulin chain, e.g., an antibody that comprises two heavy immunoglobulin chains and two light immunoglobulin chains, co-expression of the chains in a single host cell leads to association of the chains, e.g., in the cell or on the cell surface or outside the cell if such chains are secreted, so as to form the antibody or antigen-binding fragment molecule. The methods include those wherein only a heavy immunoglobulin chain or only a light immunoglobulin chain (e.g., any of those discussed herein including mature fragments and/or variable domains thereof) is expressed. Such chains are useful, for example, as intermediates in the expression of an antibody or antigen-binding fragment that includes such a chain. The present invention includes the products of such expression methods (e.g., antibodies, antigen-binding fragments, V_(H)s, or V_(L)s).

Preparation of Human Antibodies

Methods for generating human antibodies in transgenic mice are known in the art. Any such known methods can be used in the context of the present invention to make human antibodies that specifically bind to Hemolysin A.

Using VELOCIMMUNE™ technology (see, for example, U.S. Pat. No. 6,596,541, Regeneron Pharmaceuticals, VELOCIMMUNE®) or any other known method for generating monoclonal antibodies, high affinity chimeric antibodies to Hemolysin A are initially isolated having a human variable region and a mouse constant region. The VELOCIMMUNE® technology involves generation of a transgenic mouse having a genome comprising human heavy and light chain variable regions operably linked to endogenous mouse constant region loci such that the mouse produces an antibody comprising a human variable region and a mouse constant region in response to antigenic stimulation. The DNA encoding the variable regions of the heavy and light chains of the antibody are isolated and operably linked to DNA encoding the human heavy and light chain constant regions. The DNA is then expressed in a cell capable of expressing the fully human antibody.

Generally, a VELOCIMMUNE® mouse is challenged with the antigen of interest, and lymphatic cells (such as B-cells) are recovered from the mice that express antibodies. The lymphatic cells may be fused with a myeloma cell line to prepare immortal hybridoma cell lines, and such hybridoma cell lines are screened and selected to identify hybridoma cell lines that produce antibodies specific to the antigen of interest. DNA encoding the variable regions of the heavy chain and light chain may be isolated and linked to desirable isotypic constant regions of the heavy chain and light chain. Such an antibody protein may be produced in a cell, such as a CHO cell. Alternatively, DNA encoding the antigen-specific chimeric antibodies or the variable domains of the light and heavy chains may be isolated directly from antigen-specific lymphocytes.

Initially, high-affinity chimeric antibodies are isolated having a human variable region and a mouse constant region. As in the experimental section below, the antibodies are characterized and selected for desirable characteristics, including affinity, selectivity, epitope, etc. The mouse constant regions are replaced with a desired human constant region to generate the fully human antibody of the invention, for example wild type or modified IgG1 or IgG4. While the constant region selected may vary according to specific use, high affinity antigen-binding and target specificity characteristics reside in the variable region.

In general, the antibodies of the instant invention possess very high affinities, typically possessing K_(D) of from about 10⁻¹² through about 10⁻⁷ M, when measured by binding to antigen either immobilized on solid phase or in solution phase. The mouse constant regions are replaced with desired human constant regions to generate the fully human antibodies of the invention. While the constant region selected may vary according to specific use, high affinity antigen-binding and target specificity characteristics reside in the variable region.

Bioequivalents

The anti-Hemolysin A antibodies and antibody fragments of the present invention encompass proteins having amino acid sequences that vary from those of the described antibodies, but that retain the ability to bind Hemolysin A. Such variant antibodies and antibody fragments comprise one or more additions, deletions, or substitutions of amino acids when compared to parent sequence, but exhibit biological activity that is essentially equivalent to that of the described antibodies. Likewise, the antibody-encoding DNA sequences of the present invention encompass sequences that comprise one or more additions, deletions, or substitutions of nucleotides when compared to the disclosed sequence, but that encode an antibody or antibody fragment that is essentially bioequivalent to an antibody or antibody fragment of the invention.

Two antigen-binding proteins, or antibodies, are considered bioequivalent if, for example, they are pharmaceutical equivalents or pharmaceutical alternatives whose rate and extent of absorption do not show a significant difference when administered at the same molar dose under similar experimental conditions, either single dose or multiple doses. Some antibodies will be considered equivalents or pharmaceutical alternatives if they are equivalent in the extent of their absorption but not in their rate of absorption and yet may be considered bioequivalent because such differences in the rate of absorption are intentional and are reflected in the labeling, are not essential to the attainment of effective body drug concentrations on, e.g., chronic use, and are considered medically insignificant for the particular drug product studied.

In one embodiment, two antigen-binding proteins are bioequivalent if there are no clinically meaningful differences in their safety, purity, and potency.

In one embodiment, two antigen-binding proteins are bioequivalent if a patient can be switched one or more times between the reference product and the biological product without an expected increase in the risk of adverse effects, including a clinically significant change in immunogenicity, or diminished effectiveness, as compared to continued therapy without such switching.

In one embodiment, two antigen-binding proteins are bioequivalent if they both act by a common mechanism or mechanisms of action for the condition or conditions of use, to the extent that such mechanisms are known.

Bioequivalence may be demonstrated by in vivo and/or in vitro methods. Bioequivalence measures include, e.g., (a) an in vivo test in humans or other mammals, in which the concentration of the antibody or its metabolites is measured in blood, plasma, serum, or other biological fluid as a function of time; (b) an in vitro test that has been correlated with and is reasonably predictive of human in vivo bioavailability data; (c) an in vivo test in humans or other mammals in which the appropriate acute pharmacological effect of the antibody (or its target) is measured as a function of time; and (d) in a well-controlled clinical trial that establishes safety, efficacy, or bioavailability or bioequivalence of an antibody.

Bioequivalent variants of the antibodies of the invention may be constructed by, for example, making various substitutions of residues or sequences or deleting terminal or internal residues or sequences not needed for biological activity. For example, cysteine residues not essential for biological activity can be deleted or replaced with other amino acids to prevent formation of unnecessary or incorrect intramolecular disulfide bridges upon renaturation. In other contexts, bioequivalent antibodies may include antibody variants comprising amino acid changes, which modify the glycosylation characteristics of the antibodies, e.g., mutations that eliminate or remove glycosylation.

Anti-Hemolysin A Antibodies Comprising Fc Variants

According to certain embodiments of the present invention, anti-Hemolysin A antibodies are provided comprising an Fc domain comprising one or more mutations which enhance or diminish antibody binding to the FcRn receptor, e.g., at acidic pH as compared to neutral pH. For example, the present invention includes anti-Hemolysin A antibodies comprising a mutation in the C_(H)2 or a C_(H)3 region of the Fc domain, wherein the mutation(s) increases the affinity of the Fc domain to FcRn in an acidic environment (e.g., in an endosome where pH ranges from about 5.5 to about 6.0). Such mutations may result in an increase in serum half-life of the antibody when administered to an animal. Non-limiting examples of such Fc modifications include, e.g., a modification at position 250 (e.g., E or Q); 250 and 428 (e.g., L or F); 252 (e.g., L/Y/F/W or T), 254 (e.g., S or T), and 256 (e.g., S/R/Q/E/D or T); or a modification at position 428 and/or 433 (e.g., H/L/R/S/P/Q or K) and/or 434 (e.g., A, W, H, F or Y [N434A, N434W, N434H, N434F or N434Y]); or a modification at position 250 and/or 428; or a modification at position 307 or 308 (e.g., 308F, V308F), and 434. In one embodiment, the modification comprises a 428L (e.g., M428L) and 434S (e.g., N434S) modification; a 428L, 259I (e.g., V259I), and 308F (e.g., V308F) modification; a 433K (e.g., H433K) and a 434 (e.g., 434Y) modification; a 252, 254, and 256 (e.g., 252Y, 254T, and 256E) modification; a 250Q and 428L modification (e.g., T250Q and M428L); and a 307 and/or 308 modification(s) (e.g., 308F and/or 308P). In yet another embodiment, the modification comprises a 265A (e.g., D265A) and/or a 297A (e.g., N297A) modification.

For example, the present invention includes anti-Hemolysin A antibodies comprising an Fc domain comprising one or more pairs or groups of mutations selected from the group consisting of: 250Q and 248L (e.g., T250Q and M248L); 252Y, 254T and 256E (e.g., M252Y, S254T and T256E); 428L and 434S (e.g., M428L and N434S); 257I and 311I (e.g., P257I and Q311I); 257I and 434H (e.g., P257I and N434H); 376V and 434H (e.g., D376V and N434H); 307A, 380A and 434A (e.g., T307A, E380A and N434A); and 433K and 434F (e.g., H433K and N434F). All possible combinations of the foregoing Fc domain mutations, and other mutations within the antibody variable domains disclosed herein, are contemplated within the scope of the present invention.

The present invention also includes anti-Hemolysin A antibodies comprising a chimeric heavy chain constant (C_(H)) region, wherein the chimeric C_(H) region comprises segments derived from the C_(H) regions of more than one immunoglobulin isotype. For example, the antibodies of the invention may comprise a chimeric C_(H) region comprising part or all of a C_(H)2 domain derived from a human IgG1, human IgG2 or human IgG4 molecule, combined with part or all of a C_(H)3 domain derived from a human IgG1, human IgG2 or human IgG4 molecule. According to certain embodiments, the antibodies of the invention comprise a chimeric C_(H) region having a chimeric hinge region. For example, a chimeric hinge may comprise an “upper hinge” amino acid sequence (amino acid residues from positions 216 to 227 according to EU numbering) derived from a human IgG1, a human IgG2 ora human IgG4 hinge region, combined with a “lower hinge” sequence (amino acid residues from positions 228 to 236 according to EU numbering) derived from a human IgG1, a human IgG2 or a human IgG4 hinge region. According to certain embodiments, the chimeric hinge region comprises amino acid residues derived from a human IgG1 or a human IgG4 upper hinge and amino acid residues derived from a human IgG2 lower hinge. An antibody comprising a chimeric C_(H) region as described herein may, in certain embodiments, exhibit modified Fc effector functions without adversely affecting the therapeutic or pharmacokinetic properties of the antibody. (See, e.g., U.S. Provisional Appl. No. 61/759,578, filed Feb. 1, 2013, the disclosure of which is hereby incorporated by reference in its entirety).

The present invention also includes anti-Hemolysin A antibodies comprising a modified heavy chain constant (C_(H)) regions in which one or more substitutions (e.g., mutations) that interfere with the binding of Protein A have been introduced. For example, in some embodiments, anti-Hemolysin A antibodies of the invention have an IgG1 constant regions in which His435 has been mutated to Arg. With this point mutation in the heavy chain constant regions, an anti-Hemolysin A antibody of the invention would not bind to Protein A. In other embodiments of the invention, anti-Hemolysin A antibodies contain a dipeptide mutation, H435R/Y436F (EU numbering; H95R/Y96F by IMGT) in the heavy chain constant regions in order to abrogate Protein A binding. (See, e.g., U.S. Pat. No. 8,586,713, filed Jun. 25, 2010, the disclosure of which is hereby incorporated by reference in its entirety.)

Biological Characteristics of the Antibodies

In general, the antibodies of the present invention may function by binding to Hemolysin A. In some embodiments, the antibodies of the present invention may bind to another antigen (cross-reactive antibodies).

In certain embodiments, antibodies of the present invention may bind to other bacterial toxins or toxin subunits, in addition to Hemolysin A. Additional toxins or toxin subunits of S. aureus to which antibodies of the present invention may bind include bicomponent pore-forming leukotoxins (e.g., leuckocidins or gamma hemolysin) and/or S or F subunits of these toxins (e.g., LukF, LukD, and/or HlgB). In certain embodiments, antibodies of the present invention only show significant binding to Hemolysin A. In certain embodiments, antibodies of the present invention only bind detectably to Hemolysin A.

In certain embodiments, the antibodies of the present invention may be bi-specific antibodies. The bi-specific antibodies of the invention may bind one epitope in one domain and may also bind one epitope in a second domain of Hemolysin A. In certain embodiments, the bi-specific antibodies of the invention may bind two different epitopes in the same domain.

In one embodiment, the invention provides a fully human monoclonal antibody or antigen-binding fragment thereof that binds to Hemolysin A, wherein the antibody or fragment thereof exhibits one or more of the following characteristics: (i) comprises a HCVR having an amino acid sequence selected from the group consisting of SEQ ID NO: 2, 22, 42, 62, 82, 102, 122, 142, 162, 182, 202, 222, 242, 262, and 282, or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity; (ii) comprises a LCVR having an amino acid sequence selected from the group consisting of SEQ ID NO: 10, 30, 50, 70, 90, 110, 130, 150, 170, 190, 210, 230, 250, and 270, or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity; (iii) comprises a HCDR3 domain having an amino acid sequence selected from the group consisting of SEQ ID NO: 8, 28, 48, 68, 88, 108, 128, 148, 168, 188, 208, 228, 248, 268, and 288, or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity; and a LCDR3 domain having an amino acid sequence selected from the group consisting of SEQ ID NO: 16, 36, 56, 76, 96, 116, 136, 156, 176, 196, 216, 236, 256, and 276, or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity; (iv) comprises a HCDR1 domain having an amino acid sequence selected from the group consisting of SEQ ID NO: 4, 24, 44, 64, 84, 104, 124, 144, 164, 184, 204, 224, 244, 264, and 284, or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity; a HCDR2 domain having an amino acid sequence selected from the group consisting of SEQ ID NO: 6, 26, 46, 66, 86, 106, 126, 146, 166, 186, 206, 226, 246, 266, and 286, or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity; a LCDR1 domain having an amino acid sequence selected from the group consisting of SEQ ID NO: 12, 32, 52, 72, 92, 112, 132, 152, 172, 192, 212, 232, 252, and 272, or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity; and a LCDR2 domain having an amino acid sequence selected from the group consisting of SEQ ID NO: 14, 34, 54, 74, 94, 114, 134, 154, 174, 194, 214, 234, 254, and 274, or a substantially similar sequence thereof having at least 90%, at least 95%, at least 98% or at least 99% sequence identity; and (v) binds to Hemolysin A with a Ko equal to or less than 10⁻⁷.

Certain anti-Hemolysin A antibodies of the present invention are able to bind to and neutralize the activity of Hemolysin A, as determined by in vitro or in vivo assays. The ability of the antibodies of the invention to bind to and neutralize the activity of Hemolysin A may be measured using any standard method known to those skilled in the art, including binding assays, or activity assays, as described herein.

Non-limiting, exemplary in vitro assays for measuring binding activity are illustrated in Example 3 and 4, herein. In Example 6, the binding affinities and kinetic constants of human anti-Hemolysin A antibodies were determined by surface plasmon resonance and the measurements were conducted on a T200 Biacore instrument. Example 5 describes neutralization of the S. aureus Hemolysin A using Hemolysin A-specific antibodies.

The present invention also includes anti-Hemolysin A antibodies and antigen binding fragments thereof which bind to at least one biologically active fragment of any of the following proteins, or peptides: SEQ ID NO: 291 (full length wild type Hemolysin A), or SEQ ID NO: 295 (modified form of Hemolysin A). Any of the Hemolysin A peptides described herein, or fragments thereof, may be used to generate anti-Hemolysin A antibodies.

The peptides may be modified to include addition or substitution of certain residues for tagging or for purposes of conjugation to carrier molecules, such as, KLH. For example, a cysteine may be added at either the N-terminal or C-terminal end of a peptide, or a linker sequence may be added to prepare the peptide for conjugation to, for example, KLH for immunization.

The antibodies specific for Hemolysin A may contain no additional labels or moieties, or they may contain an N-terminal or C-terminal label or moiety. In one embodiment, the label or moiety is biotin. In a binding assay, the location of a label (if any) may determine the orientation of the peptide relative to the surface upon which the peptide is bound. For example, if a surface is coated with avidin, a peptide containing an N-terminal biotin will be oriented such that the C-terminal portion of the peptide will be distal to the surface. In one embodiment, the label may be a radionuclide, a fluorescent dye or a MRI-detectable label. In certain embodiments, such labeled antibodies may be used in diagnostic assays including imaging assays.

Epitope Mapping and Related Technologies

The present invention includes anti-Hemolysin A antibodies which interact with one or more amino acids found within one or more regions of Hemolysin A. The epitope to which the antibodies bind may consist of a single contiguous sequence of 3 or more (e.g., 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more) amino acids located within any of the aforementioned regions of the Hemolysin A molecule (e.g. a linear epitope in a domain). Alternatively, the epitope may consist of a plurality of non-contiguous amino acids (or amino acid sequences) located within either or both of the aforementioned regions of the Hemolysin A molecule (e.g. a conformational epitope).

Various techniques known to persons of ordinary skill in the art can be used to determine whether an antibody “interacts with one or more amino acids” within a polypeptide or protein. Exemplary techniques include, for example, routine cross-blocking assays, such as that described in Antibodies, Harlow and Lane (Cold Spring Harbor Press, Cold Spring Harbor, N.Y.). Other methods include alanine scanning mutational analysis, peptide blot analysis (Reineke (2004) Methods Mol Biol 248:443-63), peptide cleavage analysis, crystallographic studies and NMR analysis. In addition, methods such as epitope excision, epitope extraction and chemical modification of antigens can be employed (Tomer (2000) Protein Science 9: 487-496). Another method that can be used to identify the amino acids within a polypeptide with which an antibody interacts is hydrogen/deuterium exchange detected by mass spectrometry. In general terms, the hydrogen/deuterium exchange method involves deuterium-labeling the protein of interest, followed by binding the antibody to the deuterium-labeled protein. Next, the protein/antibody complex is transferred to water and exchangeable protons within amino acids that are protected by the antibody complex undergo deuterium-to-hydrogen back-exchange at a slower rate than exchangeable protons within amino acids that are not part of the interface. As a result, amino acids that form part of the protein/antibody interface may retain deuterium and therefore exhibit relatively higher mass compared to amino acids not included in the interface. After dissociation of the antibody, the target protein is subjected to protease cleavage and mass spectrometry analysis, thereby revealing the peptides containing the deuterium-labeled residues that contain specific amino acids with which the antibody interacts. See, e.g., Ehring (1999) Analytical Biochemistry 267(2):252-259; Engen and Smith (2001) Anal. Chem. 73: 256A-265A.

The term “epitope” refers to a site on an antigen to which B and/or T cells respond. B-cell epitopes can be formed both from contiguous amino acids or noncontiguous amino acids juxtaposed by tertiary folding of a protein. Epitopes formed from contiguous amino acids are typically retained on exposure to denaturing solvents, whereas epitopes formed by tertiary folding are typically lost on treatment with denaturing solvents. An epitope typically includes at least 3, and more usually, at least 5 or 8-10 amino acids in a unique spatial conformation.

Modification-Assisted Profiling (MAP), also known as Antigen Structure-based Antibody Profiling (ASAP) is a method that categorizes large numbers of monoclonal antibodies (mAbs) directed against the same antigen according to the similarities of the binding profile of each antibody to chemically or enzymatically modified antigen surfaces (see US 2004/0101920, herein specifically incorporated by reference in its entirety). Each category may reflect a unique epitope either distinctly different from or partially overlapping with epitope represented by another category. This technology allows rapid filtering of genetically identical antibodies, such that characterization can be focused on genetically distinct antibodies. When applied to hybridoma screening, MAP may facilitate identification of rare hybridoma clones that produce mAbs having the desired characteristics. MAP may be used to sort the antibodies of the invention into groups of antibodies binding different epitopes.

In certain embodiments, the anti-Hemolysin A antibodies or antigen-binding fragments thereof bind an epitope within any one or more of the regions exemplified in wild type Hemolysin A, as exemplified in SEQ ID NO: 291, or modified Hemolysin A, as exemplified in SEQ ID NO: 295, or to a fragment thereof.

The present invention includes human anti-Hemolysin A antibodies that bind to the same epitope, or a portion of the epitope, as any of the specific exemplary antibodies described herein, or an antibody having the CDR sequences of any of the exemplary antibodies described herein. Likewise, the present invention also includes anti-Hemolysin A antibodies that compete for binding to Hemolysin A or a Hemolysin A fragment with any of the specific exemplary antibodies described herein, or an antibody having the CDR sequences of any of the exemplary antibodies described herein.

One can easily determine whether an antibody binds to the same epitope as, or competes for binding with, a reference anti-Hemolysin A antibody by using routine methods known in the art. For example, to determine if a test antibody binds to the same epitope as a reference anti-Hemolysin A antibody of the invention, the reference antibody is allowed to bind to a Hemolysin A protein or peptide under saturating conditions. Next, the ability of a test antibody to bind to the Hemolysin A molecule is assessed. If the test antibody is able to bind to Hemolysin A following saturation binding with the reference anti-Hemolysin A antibody, it can be concluded that the test antibody binds to a different epitope than the reference anti-hemolysin A antibody. On the other hand, if the test antibody is not able to bind to the Hemolysin A protein following saturation binding with the reference anti-Hemolysin A antibody, then the test antibody may bind to the same epitope as the epitope bound by the reference anti-Hemolysin A antibody of the invention.

To determine if an antibody competes for binding with a reference anti-Hemolysin A antibody, the above-described binding methodology is performed in two orientations: In a first orientation, the reference antibody is allowed to bind to a Hemolysin A protein under saturating conditions followed by assessment of binding of the test antibody to the Hemolysin A molecule. In a second orientation, the test antibody is allowed to bind to a Hemolysin A molecule under saturating conditions followed by assessment of binding of the reference antibody to the Hemolysin A molecule. If, in both orientations, only the first (saturating) antibody is capable of binding to the Hemolysin A molecule, then it is concluded that the test antibody and the reference antibody compete for binding to Hemolysin A. As will be appreciated by a person of ordinary skill in the art, an antibody that competes for binding with a reference antibody may not necessarily bind to the identical epitope as the reference antibody, but may sterically block binding of the reference antibody by binding an overlapping or adjacent epitope.

Two antibodies bind to the same or overlapping epitope if each competitively inhibits (blocks) binding of the other to the antigen. That is, a 1-, 5-, 10-, 20- or 100-fold excess of one antibody inhibits binding of the other by at least 50% but preferably 75%, 90% or even 99% as measured in a competitive binding assay (see, e.g., Junghans et al., Cancer Res. 1990 50:1495-1502). Alternatively, two antibodies have the same epitope if essentially all amino acid mutations in the antigen that reduce or eliminate binding of one antibody reduce or eliminate binding of the other. Two antibodies have overlapping epitopes if some amino acid mutations that reduce or eliminate binding of one antibody reduce or eliminate binding of the other.

Additional routine experimentation (e.g., peptide mutation and binding analyses) can then be carried out to confirm whether the observed lack of binding of the test antibody is in fact due to binding to the same epitope as the reference antibody or if steric blocking (or another phenomenon) is responsible for the lack of observed binding. Experiments of this sort can be performed using ELISA, RIA, surface plasmon resonance, flow cytometry or any other quantitative or qualitative antibody-binding assay available in the art.

Immunoconjugates

The invention encompasses a human anti-Hemolysin A monoclonal antibody conjugated to a therapeutic moiety (“immunoconjugate”), such as an agent that is capable of reducing the severity of Staphylococcus aureus infection, or to ameliorate at least one symptom associated with S. aureus infection, or the severity thereof. As used herein, the term “immunoconjugate” refers to an antibody that is chemically or biologically linked to a radioactive agent, a cytokine, an interferon, a target or reporter moiety, an enzyme, a toxin, or a therapeutic agent. The antibody may be linked to the radioactive agent, cytokine, interferon, target or reporter moiety, enzyme, toxin, or therapeutic agent at any location along the molecule so long as it is able to bind its target. An example of immunoconjugate is an antibody drug conjugate. In some embodiments, the agent may be a second different antibody to Hemolysin A, or to a cytokine such as IL-1, IL-6, or a chemokine such as TGF-β. The type of therapeutic moiety that may be conjugated to the anti-Hemolysin A antibody will take into account the condition to be treated and the desired therapeutic effect to be achieved. Examples of suitable agents for forming immunoconjugates are known in the art; see for example, WO 05/103081. The preparation of immunoconjugates and immunotoxins is generally well known in the art (see, e.g., U.S. Pat. No. 4,340,535). Immunoconjugates are described in detail, for example, in U.S. Pat. Nos. 7,250,492, 7,420,040 and 7,411,046, each of which is incorporated herein in their entirety.

Multi-Specific Antibodies

The antibodies of the present invention may be mono-specific, bi-specific, or multi-specific. Multi-specific antibodies may be specific for different epitopes of one target polypeptide or may contain antigen-binding domains specific for more than one target polypeptide. See, e.g., Tutt et al., 1991, J. Immunol. 147:60-69; Kufer et al., 2004, Trends Biotechnol. 22:238-244. The antibodies of the present invention can be linked to or co-expressed with another functional molecule, e.g., another peptide or protein. For example, an antibody or fragment thereof can be functionally linked (e.g., by chemical coupling, genetic fusion, noncovalent association or otherwise) to one or more other molecular entities, such as another antibody or antibody fragment to produce a bi-specific or a multi-specific antibody with a second binding specificity. For example, the present invention includes bi-specific antibodies wherein one arm of an immunoglobulin is specific for the N-terminal region of Hemolysin A, or a fragment thereof, and the other arm of the immunoglobulin is specific for the C-terminal region of Hemolysin A, or a second therapeutic target, or is conjugated to a therapeutic moiety. An exemplary bi-specific antibody format that can be used in the context of the present invention involves the use of a first immunoglobulin (Ig) C_(H3) domain and a second Ig C_(H3) domain, wherein the first and second Ig C_(H3) domains differ from one another by at least one amino acid, and wherein at least one amino acid difference reduces binding of the bi-specific antibody to Protein A as compared to a bi-specific antibody lacking the amino acid difference. In one embodiment, the first Ig C_(H3) domain binds Protein A and the second Ig C_(H3) domain contains a mutation that reduces or abolishes Protein A binding such as an H95R modification (by IMGT exon numbering; H435R by EU numbering). The second C_(H3) may further comprise a Y96F modification (by IMGT; Y436F by EU). Further modifications that may be found within the second C_(H3) include: D16E, L18M, N44S, K52N, V57M, and V82I (by IMGT; D356E, L358M, N384S, K392N, V397M, and V422I by EU) in the case of IgG1 antibodies; N44S, K52N, and V82I (IMGT; N384S, K392N, and V422I by EU) in the case of IgG2 antibodies; and Q15R, N44S, K52N, V57M, R69K, E79Q, and V82I (by IMGT; Q355R, N384S, K392N, V397M, R409K, E419Q, and V422I by EU) in the case of IgG4 antibodies. Variations on the bi-specific antibody format described above are contemplated within the scope of the present invention.

Other exemplary bispecific formats that can be used in the context of the present invention include, without limitation, e.g., scFv-based or diabody bispecific formats, IgG-scFv fusions, dual variable domain (DVD)-Ig, Quadroma, knobs-into-holes, common light chain (e.g., common light chain with knobs-into-holes, etc.), CrossMab, CrossFab, (SEED)body, leucine zipper, Duobody, IgG1/IgG2, dual acting Fab (DAF)-IgG, and Mab² bispecific formats (see, e.g., Klein et al. 2012, mAbs 4:6, 1-11, and references cited therein, for a review of the foregoing formats). Bispecific antibodies can also be constructed using peptide/nucleic acid conjugation, e.g., wherein unnatural amino acids with orthogonal chemical reactivity are used to generate site-specific antibody-oligonucleotide conjugates which then self-assemble into multimeric complexes with defined composition, valency and geometry. (See, e.g., Kazane et al., J. Am. Chem. Soc. [Epub: Dec. 4, 2012]).

Therapeutic Administration and Formulations

The invention provides therapeutic compositions comprising the anti-Hemolysin A antibodies or antigen-binding fragments thereof as discussed herein. The therapeutic compositions in accordance with the invention can be administered with suitable carriers, excipients, and other agents that are incorporated into formulations to provide improved transfer, delivery, tolerance, and the like. A multitude of appropriate formulations can be found in the formulary known to all pharmaceutical chemists: Remington's Pharmaceutical Sciences, Mack Publishing Company, Easton, Pa. These formulations include, for example, powders, pastes, ointments, jellies, waxes, oils, lipids, lipid (cationic or anionic) containing vesicles (such as LIPOFECTIN™), DNA conjugates, anhydrous absorption pastes, oil-in-water and water-in-oil emulsions, emulsions carbowax (polyethylene glycols of various molecular weights), semi-solid gels, and semi-solid mixtures containing carbowax. See also Powell et al. “Compendium of excipients for parenteral formulations” PDA (1998) J Pharm Sci Technol 52:238-311.

The dose of antibody may vary depending upon the age and the size of a subject to be administered, target disease, conditions, route of administration, and the like. When the antibody of the present invention is used for preventing or treating dermonecrosis, skin and soft-tissue infections (including abscesses), surgical site infections, prosthetic joint infections, bacteremia, septicemia, septic arthritis, meningitis, osteomyelitis, endocarditis, pneumonia, toxic shock syndrome, mastitis, or furunculosis and carbunculosis (boils) in an adult patient, or for preventing or treating an S. aureus infection, it is advantageous to intravenously administer the antibody of the present invention normally at a single dose of about 0.1 to about 100 mg/kg body weight, more preferably about 5 to about 100, about 10 to about 90, or about 20 to about 70 mg/kg body weight. Depending on the severity of the condition, the frequency and the duration of the treatment can be adjusted. In certain embodiments, the antibody or antigen-binding fragment thereof of the invention can be administered as an initial dose of at least about 0.1 mg to about 800 mg, about 1 to about 500 mg, about 5 to about 300 mg, or about 10 to about 200 mg, to about 100 mg, or to about 50 mg. In certain embodiments, the initial dose may be followed by administration of a second or a plurality of subsequent doses of the antibody or antigen-binding fragment thereof in an amount that can be approximately the same or less than that of the initial dose, wherein the subsequent doses are separated by at least 1 day to 3 days; at least one week, at least 2 weeks; at least 3 weeks; at least 4 weeks; at least 5 weeks; at least 6 weeks; at least 7 weeks; at least 8 weeks; at least 9 weeks; at least 10 weeks; at least 12 weeks; or at least 14 weeks.

Various delivery systems are known and can be used to administer the pharmaceutical composition of the invention, e.g., encapsulation in liposomes, microparticles, microcapsules, recombinant cells capable of expressing the mutant viruses, receptor mediated endocytosis (see, e.g., Wu et al. (1987) J. Biol. Chem. 262:4429-4432). Methods of introduction include, but are not limited to, intradermal, transdermal, intramuscular, intraperitoneal, intravenous, subcutaneous, intranasal, epidural and oral routes. The composition may be administered by any convenient route, for example by infusion or bolus injection, by absorption through epithelial or mucocutaneous linings (e.g., oral mucosa, rectal and intestinal mucosa, etc.) and may be administered together with other biologically active agents. Administration can be systemic or local. The pharmaceutical composition can be also delivered in a vesicle, in particular a liposome (see, for example, Langer (1990) Science 249:1527-1533).

The use of nanoparticles to deliver the antibodies of the present invention is also contemplated herein. Antibody-conjugated nanoparticles may be used both for therapeutic and diagnostic applications. Antibody-conjugated nanoparticles and methods of preparation and use are described in detail by Arruebo, M., et al. 2009 (“Antibody-conjugated nanoparticles for biomedical applications” in J. Nanomat. Volume 2009, Article ID 439389, 24 pages, doi: 10.1155/2009/439389), incorporated herein by reference. Nanoparticles for drug delivery have also been described in, for example, U.S. Pat. Nos. 8,277,812, 8,258,256, 8,257,740, 8,246,995, 8,236,330, each incorporated herein in its entirety.

In certain situations, the pharmaceutical composition can be delivered in a controlled release system. In one embodiment, a pump may be used. In another embodiment, polymeric materials can be used. In yet another embodiment, a controlled release system can be placed in proximity of the composition's target, thus requiring only a fraction of the systemic dose.

The injectable preparations may include dosage forms for intravenous, subcutaneous, intracutaneous and intramuscular injections, drip infusions, etc. These injectable preparations may be prepared by methods publicly known. For example, the injectable preparations may be prepared, e.g., by dissolving, suspending or emulsifying the antibody or its salt described above in a sterile aqueous medium or an oily medium conventionally used for injections. As the aqueous medium for injections, there are, for example, physiological saline, an isotonic solution containing glucose and other auxiliary agents, etc., which may be used in combination with an appropriate solubilizing agent such as an alcohol (e.g., ethanol), a polyalcohol (e.g., propylene glycol, polyethylene glycol), a nonionic surfactant [e.g., polysorbate 80, HCO-50 (polyoxyethylene (50 mol) adduct of hydrogenated castor oil)], etc. As the oily medium, there are employed, e.g., sesame oil, soybean oil, etc., which may be used in combination with a solubilizing agent such as benzyl benzoate, benzyl alcohol, etc. The injection thus prepared is preferably filled in an appropriate ampoule.

A pharmaceutical composition of the present invention can be delivered subcutaneously or intravenously with a standard needle and syringe. In addition, with respect to subcutaneous delivery, a pen delivery device readily has applications in delivering a pharmaceutical composition of the present invention. Such a pen delivery device can be reusable or disposable. A reusable pen delivery device generally utilizes a replaceable cartridge that contains a pharmaceutical composition. Once all of the pharmaceutical composition within the cartridge has been administered and the cartridge is empty, the empty cartridge can readily be discarded and replaced with a new cartridge that contains the pharmaceutical composition. The pen delivery device can then be reused. In a disposable pen delivery device, there is no replaceable cartridge. Rather, the disposable pen delivery device comes prefilled with the pharmaceutical composition held in a reservoir within the device. Once the reservoir is emptied of the pharmaceutical composition, the entire device is discarded.

Numerous reusable pen and autoinjector delivery devices have applications in the subcutaneous delivery of a pharmaceutical composition of the present invention. Examples include, but certainly are not limited to AUTOPEN™ (Owen Mumford, Inc., Woodstock, UK), DISETRONIC™ pen (Disetronic Medical Systems, Burghdorf, Switzerland), HUMALOG MIX 75/25™ pen, HUMALOG™ pen, HUMALIN 70/30™ pen (Eli Lilly and Co., Indianapolis, Ind.), NOVOPEN™ I, II and III (Novo Nordisk, Copenhagen, Denmark), NOVOPEN JUNIOR™ (Novo Nordisk, Copenhagen, Denmark), BD™ pen (Becton Dickinson, Franklin Lakes, N.J.), OPTIPEN™, OPTIPEN PRO™, OPTIPEN STARLET™, and OPTICLIK™ (Sanofi-aventis, Frankfurt, Germany), to name only a few. Examples of disposable pen delivery devices having applications in subcutaneous delivery of a pharmaceutical composition of the present invention include, but certainly are not limited to the SOLOSTAR™ pen (Sanofi-aventis), the FLEXPEN™ (Novo Nordisk), and the KWIKPEN™ (Eli Lilly), the SURECLICK™ Autoinjector (Amgen, Thousand Oaks, Calif.), the PENLET™ (Haselmeier, Stuttgart, Germany), the EPIPEN (Dey, L. P.) and the HUMIRA™ Pen (Abbott Labs, Abbott Park, Ill.), to name only a few.

Advantageously, the pharmaceutical compositions for oral or parenteral use described above are prepared into dosage forms in a unit dose suited to fit a dose of the active ingredients. Such dosage forms in a unit dose include, for example, tablets, pills, capsules, injections (ampoules), suppositories, etc. The amount of the aforesaid antibody contained is generally about 5 to about 500 mg per dosage form in a unit dose; especially in the form of injection, it is preferred that the aforesaid antibody is contained in about 5 to about 100 mg and in about 10 to about 250 mg for the other dosage forms. The present invention includes an injection device (e.g., a pre-filled syringe or pre-filled autoinjector) or a vial (e.g., a glass or plastic vial) comprising an antibody or antigen-binding fragment of the present invention or pharmaceutical composition thereof which includes a pharmaceutically acceptable carrier.

Therapeutic Uses of the Antibodies

In certain embodiments of the invention, the present antibodies are useful for treating a Staphylococcus aureus infection, or at least one symptom associated with S. aureus infection. In some embodiments, the antibodies may be useful for treating a condition or symptom of dermonecrosis, skin and soft-tissue infections (including abscesses), surgical site infections, prosthetic joint infections, bacteremia, septicemia, septic arthritis, meningitis, osteomyelitis, endocarditis, pneumonia, toxic shock syndrome, mastitis, or furunculosis and carbunculosis (boils). The antibodies of the invention are also contemplated for prophylactic use in patients at risk for developing a S. aureus infection. These patients include the elderly, or patients immunocompromised due to illness or treatment with immunosuppressive therapeutics, or patients who are at a greater risk of nosocomial infection such as post-operative patients. In various embodiments of the therapeutic uses discussed above, the S. aureus bacteria may be resistant to one or more types of antibiotic treatments. In one embodiment, the bacteria are methicillin-resistant S. aureus (MRSA). It is contemplated that the antibodies of the invention may be used alone, or in conjunction with a second agent, or third agent for treating S. aureus infection, or for alleviating at least one symptom or complication associated with S. aureus infection. The second or third agents may be delivered concurrently with the antibodies of the invention, or they may be administered separately, either before or after the antibodies of the invention. A patient that may receive an antibody or antigen-binding fragment of the invention or a pharmaceutical composition thereof includes, for example, an animal such as a mammal such as a human (e.g., an elderly human, for example, 65 years of age or older), rabbit, mouse, rat, cow, pig, dog, primate, horse or sheep.

In certain embodiments, the present antibodies are useful for reducing the number of Staphylococcus aureus bacteria in an individual or a particular tissue or organ of the individual. In some embodiments, the S. aureus bacteria may be resistant to one or more types of antibiotic treatments. In one embodiment, the bacteria are methicillin-resistant S. aureus (MRSA). In certain embodiments, the present antibodies are useful for reducing the toxic activities of Hemolysin A produced by Staphylococcus aureus bacteria in an individual reducing the symptoms produced by the infection, and permitting other pharmaceutical agents and/or the immune system of the patient to control the infection.

In a further embodiment of the invention the present antibodies are used for the preparation of a pharmaceutical composition for treating patients suffering from Staphylococcus aureus infection, or a symptom associated with S. aureus infection.

Combination Therapies

Combination therapies may include an anti-Hemolysin A antibody of the invention and any additional therapeutic agent(s) that may be advantageously combined with an antibody of the invention, or with a biologically active fragment of an antibody of the invention.

The antibodies may be used in conjunction with other therapies, such as antibiotics NSAIDs, antibody LTM14, antibody LC10, corticosteroids or prednisone.

The additional therapeutically active component(s) may be administered prior to, concurrent with, or after the administration of the anti-Hemolysin A antibody of the present invention. For purposes of the present disclosure, such administration regimens are considered the administration of an anti-Hemolysin A antibody “in combination with” one or more additional therapeutically active component(s).

Diagnostic Uses of the Antibodies

The anti-Hemolysin A antibodies of the present invention may also be used to detect and/or measure Hemolysin A in a sample, e.g., for diagnostic purposes. It is envisioned that any one or more of the antibodies of the invention may be used to detect the presence and severity of Staphylococcus aureus infection. Exemplary diagnostic assays for Hemolysin A may comprise, e.g., contacting a sample, obtained from a patient, with an anti-Hemolysin A antibody of the invention, wherein the anti-Hemolysin A antibody is labeled with a detectable label or reporter molecule or used as a capture ligand to selectively isolate Hemolysin A from patient samples. Alternatively, an unlabeled anti-Hemolysin A antibody can be used in diagnostic applications in combination with a secondary antibody which is itself detectably labeled. The detectable label or reporter molecule can be a radioisotope, such as ³H, ¹⁴C, ³²P, ³⁵S, or ¹²⁵I; a fluorescent or chemiluminescent moiety such as fluorescein isothiocyanate, or rhodamine; or an enzyme such as alkaline phosphatase, β-galactosidase, horseradish peroxidase, or luciferase. Specific exemplary assays that can be used to detect or measure Hemolysin A in a sample include enzyme-linked immunosorbent assay (ELISA), radioimmunoassay (RIA), and fluorescence-activated cell sorting (FACS).

Samples that can be used in Hemolysin A diagnostic assays according to the present invention include any tissue or fluid sample obtainable from a patient, which contains detectable quantities of either Hemolysin A, or fragments thereof, under normal or pathological conditions. Generally, levels of Hemolysin A in a particular sample obtained from a healthy patient (e.g., a patient not afflicted with Staphylococcus aureus infection) will be measured to initially establish a baseline, or standard, level of Hemolysin A. This baseline level of Hemolysin A can then be compared against the levels of Hemolysin A measured in samples obtained from individuals suspected of having S. aureus infection related condition, or symptoms associated with such condition.

The antibodies specific for Hemolysin A may contain no additional labels or moieties, or they may contain an N-terminal or C-terminal label or moiety. In one embodiment, the label or moiety is biotin. In a binding assay, the location of a label (if any) may determine the orientation of the peptide relative to the surface upon which the peptide is bound. For example, if a surface is coated with avidin, a peptide containing an N-terminal biotin will be oriented such that the C-terminal portion of the peptide will be distal to the surface. In some embodiments, the label may be detectable label such as a radionuclide, a fluorescent dye or a MRI-detectable label. Detectable labels may be linked to the antibodies wherein such antibodies may be used in imaging assays.

EXAMPLES

The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how to make and use the methods and compositions of the invention, and are not intended to limit the scope of what the inventors regard as their invention. Unless indicated otherwise, parts are parts by weight, molecular weight is average molecular weight, temperature is in degrees Centigrade, and pressure is at or near atmospheric.

Example 1. Generation of Human Antibodies to Hemolysin A

Two immunogens were used to immunize mice: full-length wild type Hemolysin A (Hla) without the signal sequence (amino acids 27-391) and full length non-toxic Hemolysin A (Hla-H35L); both were recombinant His-tagged proteins expressed in E. coli and purified. In certain embodiments, antibodies that bind specifically to Hemolysin A may be prepared using fragments of the above-noted regions, or peptides that extend beyond the designated regions by about 5 to about 20 amino acid residues from either, or both, the N- or C-terminal ends of the regions described herein. In certain embodiments, any combination of the above-noted regions or fragments thereof may be used in the preparation of Hemolysin A specific antibodies. In certain embodiments, any one or more of the above-noted domains of Hemolysin A, or fragments thereof may be used for preparing monospecific, bispecific, or multispecific antibodies. H1H15375P, H1H15376P, H1H15377P, H1H15378P, H1H15379P, H1H15380P and H1H15418P2 were produced by immunization with the nontoxic Hemolysin A; and H1H15381P, H1H15399P, H1H15404P, H1H15405P, H1H15408P, H1H15410P, H1H15414P, and H1H15420P2 were produced by immunization with wild-type Hemolysin A.

The full length proteins, or fragments thereof, that were used as immunogens, as noted above, were administered directly, with an adjuvant to stimulate the immune response, to a VELOCIMMUNE® mouse comprising DNA encoding human Immunoglobulin heavy and kappa light chain variable regions. The antibody immune response was monitored by a Hemolysin A-specific immunoassay. When a desired immune response was achieved, anti-Hemolysin A antibodies were isolated directly from antigen-positive B cells without fusion to myeloma cells, as described in U.S. 2007/0280945A1, herein specifically incorporated by reference in its entirety. Using this method, several fully human anti-Hemolysin A antibodies (i.e., antibodies possessing human variable domains and human constant domains) were obtained; exemplary antibodies generated in this manner were designated as follows: H1H15375P, H1H15376P, H1H15377P, H1H15378P, H1H15379P, H1H15380P, H1H15381P, H1H15399P, H1H15404P, H1H15405P, H1H15408P, H1H15410P, H1H15414P, H1H15418P2 and H1H15420P2.

The biological properties of the exemplary antibodies generated in accordance with the methods of this Example are described in detail in the Examples set forth below.

Example 2. Heavy and Light Chain Variable Region Amino Acid Sequences

Table 1 sets forth the heavy and light chain variable region amino acid sequence pairs of selected antibodies specific for Hemolysin A and their corresponding antibody identifiers. Antibodies are typically referred to herein according to the following nomenclature: Fc prefix (e.g. “H4H”, “H2M”), followed by a numerical identifier (e.g., “5375” as shown in Table 1), followed by a “P” or “N” suffix. Thus, according to this nomenclature, an antibody may be referred to as, e.g., “H1H5375”. The H4H, H1M, and H2M prefixes on the antibody designations used herein indicate the particular Fc region of the antibody. For example, an “H2M” antibody has a mouse IgG2 Fc, whereas an “H4H” antibody has a human IgG4 Fc. As will be appreciated by a person of ordinary skill in the art, an H1M or H2M antibody can be converted to an H4H antibody, and vice versa, but in any event, the variable domains (including the CDRs), which are indicated by the numerical identifiers shown in Table 1, will remain the same. Antibodies having the same numerical antibody designation, but differing by a letter suffix of N, B or P refer to antibodies having heavy and light chains with identical CDR sequences but with sequence variations in regions that fall outside of the CDR sequences (i.e., in the framework regions). Thus, N, B and P variants of a particular antibody have identical CDR sequences within their heavy and light chain variable regions but differ from one another within their framework regions.

TABLE 1 Antibody SEQ ID NOs: Designation HCVR HCDR1 HCDR2 HCDR3 LCVR LCDR1 LCDR2 LCDR3 H1H15375P 2 4 6 8 10 12 14 16 H1H15376P 22 24 26 28 30 32 34 36 H1H15377P 42 44 46 48 50 52 54 56 H1H15378P 62 64 66 68 70 72 74 76 H1H15379P 82 84 86 88 90 92 94 96 H1H15380P 102 104 106 108 110 112 114 116 H1H15381P 122 124 126 128 130 132 134 136 H1H15399P 142 144 146 148 150 152 154 156 H1H15404P 162 164 166 168 170 172 174 176 H1H15405P 182 184 186 188 190 192 194 196 H1H15408P 202 204 206 208 210 212 214 216 H1H15410P 222 224 226 228 230 232 234 236 H1H15414P 242 244 246 248 250 252 254 256 H1H15418P2 262 264 266 268 270 272 274 276 H1H15420P2 282 284 286 288 270 272 274 276

Example 3. Binding of Human Monoclonal Antibodies to S. aureus Hemolysin A Toxin

In order to determine if the antibodies of the invention were able to bind to the Hemolysin A monomer, purified antibodies (H1H15375P, H1H15376P, H1H15377P, H1H15378P, H1H15379P, H1H15380P, H1H15381P, H1H15399P, H1H15404P, H1H15405P, H1H15408P, H1H15410P, H1H15414P, H1H15418P2 and H1H15420P2) were tested by ELISA. MaxiSorp microtiter plates were coated overnight with 10 μg/mL purified S. aureus Hemolysin A per well. Titrations of invention antibodies and isotype-matched control antibody (ranging from 50 μM-1 pM with 1:3 serial dilutions) were added to toxin-containing wells and incubated for one hour at 25° C. Wells were washed three times and then incubated with 100 ng/mL anti-human HRP secondary antibody per well for one hour at 25° C. 100 μL of SuperSignal ELISA Pico Chemiluminescent Substrate, (ThermoFisher Scientific) was then added to each well and signal was detected (Victor X3 plate reader, Perkin Elmer). Luminescence values were analyzed by a three-parameter logistic equation over a 12-point response curve (GraphPad Prism).

Sub-nanomolar EC50 binding of the anti-Hemolysin A antibodies were observed for binding to S. aureus Hemolysin A toxin. (Table 2 and FIG. 1 ).

TABLE 2 Binding of anti-Hemolysin A mAbs to S. aureus Hemolysin A EC₅₀ [M] for Hemolysin A AbPID binding H1H15375P 3.94E−10 H1H15376P 3.13E−10 H1H15377P 2.92E−10 H1H15378P 2.48E−10 H1H15379P 3.24E−10 H1H15380P 3.45E−10 H1H15381P 2.85E−10 H1H15399P 3.12E−10 H1H15404P 3.02E−10 H1H15405P 5.25E−10 H1H15408P 3.56E−10 H1H15410P 3.21E−10 H1H15414P 5.40E−10 H1H15418P2 3.58E−10 H1H15420P2 3.11E−10 Isotype control NB NB, no binding

Example 4. Binding of Human mAbs to S. aureus Hemolysin A to Bicomponent Toxins

S. aureus strains can produce additional pore-forming toxins, leukocidins and gamma hemolysin (Hlg), which also require oligomerization to form functional pores. Unlike Hemolysin A, leukocidins and Hlg are bicomponent toxins composed of 2 subunits, the S-subunit and the F-subunit. Currently, five S subunits (LukA, LukE, LukS-PV, HlgA, and HlgC) and four F subunits (LukB, LukD, LukF-PV, and HlgB) have been identified resulting in five functional toxins (LukAB, LukED, PVL, HlgAB, and HlgCB). While low sequence identity is observed between the S- and F-subunits and Hemolysin A (Aman M J and Adhikaari R P, (2014) Toxins. 6:950-972), all components show structural homology with Hemolysin A.

In order to determine if the anti-Hemolysin A antibodies of the invention cross bind to other toxins, purified antibodies (H1H15375P, H1H15376P, H1H15377P, H1H15378P, H1H15379P, H1H15380P, H1H15381P, H1H15399P, H1H15404P, H1H15405P, H1H15408P, H1H15410P, H1H15414P, H1H15418P2 and H1H15420P2) were tested for cross-reactivity to S. aureus bicomponent toxins by ELISA. MaxiSorp microtiter plates were coated overnight with 10 μg/mL of individual F-components of S. aureus bicomponent toxins per well. Recombinant toxin components were either obtained from IBT BioServices (Gaithersburg, Md.) or generated by GenScript (Piscataway Township, N.J.). Titrations of invention antibodies and an isotype-matched control antibody (ranging from 50 μM-100 pM with 1:3 dilutions) were added to toxin-containing wells and incubated for 1 hour at 25° C. Wells were washed 3 times and then incubated with 100 ng/mL anti-human HRP secondary antibody per well for one hour at 25° C. 100 μL of SuperSignal ELISA Pico Chemiluminescent Substrate, (ThermoFisher Scientific) was added to the wells and signal was detected (Victor X3 plate reader, Perkin Elmer). Luminescence values were analyzed by a three-parameter logistic equation over an 11-point response curve (GraphPad Prism). Isotype-matched irrelevant control antibody and S. aureus delta toxin were included as controls.

Testing of the 15 antibodies in the invention for cross-reactivity to bicomponent toxins revealed one mAb, H1H15381P, that displayed binding to the F-components LukF, LukD and HlgB, albeit with 2-log or 3-log lower affinity than that seen with Hemolysin A (Table 3 and FIGS. 2 a-c ). When H1H15381P was tested for cross-reactivity to the S-components LukS, LukE, HlgA and HlgC, binding affinities were significantly lower compared to binding to the F-components (FIGS. 3 a-c ). H1H15381P binding is specific for Hemolysin A and bicomponent toxins, as it showed no binding to S. aureus delta toxin Isotype-matched control antibody did not demonstrate any binding to the bicomponent toxin components.

TABLE 3 Binding of anti-Hemolysin A mAbs to S. aureus bicomponent toxins (F-component only) EC₅₀ [M] for bicomponent toxin binding S. aureus LukF LukF LukD HIgB Delta AbPID (GS) (IBT) (GS) (GS) toxin H1H15375P NB — NB NB NB H1H15376P NB — NB NB NB H1H15377P NB — NB NB NB H1H15378P NB — NB NB NB H1H15379P NB — NB NB NB H1H15380P NB — NB NB NB H1H15381P 6.67E−08 1.65E−07 5.96E−08 1.021E−07 NB H1H15399P NB — NB NB NB H1H15404P NB — NB NB NB H1H15405P NB — NB NB NB H1H15408P NB — NB NB NB H1H15410P NB — NB NB NB H1H15414P NB — NB NB NB H1H15418P2 NB — NB NB NB H1H15420P2 NB — NB NB NB Isotype NB — NB NB NB control GS, GenScript; IBT, IBT BioServices; NB, no binding; —, not tested

Example 5. Neutralization of S. aureus Hemolysin A in a THP-1 Cytotoxicity Assay

The ability of purified mAbs to prevent Hemolysin A-mediated lysis was tested using the human monocyte cell line, THP-1. A total of 2.5×10⁵ THP-1 cells in RPMI (supplemented with 1% heat-inactivated FBS, L-glutamine and non-essential amino acids) were seeded into 96-well clear bottom-black tissue culture treated plates and incubated for 1 hour at 37° C. with 5% CO₂. Titrations of purified antibodies (H1H15375P, H1H15376P, H1H15377P, H1H15378P, H1H15379P, H1H15380P, H1H15381P, H1H15399P, H1H15404P, H1H15405P, H1H15408P, H1H15410P, H1H15414P, H1H15418P2 and H1H15420P2), or isotype-matched control antibody (ranging from 10-0 μM with 1:3 serial dilutions in media) were incubated with 10 nM purified Hemolysin A in a 96 well plate for 30 minutes at 25° C. on a shaker prior to addition to the plated cells. A titration of purified Hemolysin A (1.5-0 μM with 1:3 dilutions) without antibody was also incubated with cells alone.

The cells with toxin:antibody or toxin alone were then incubated for three hours (37° C., 5% CO₂) and cell death was measured using the CytoTox-Glo Assay kit (Promega). Luminescence was detected using a plate reader (Victor X3, Perkin Elmer). All antibodies of the invention displayed similar neutralization activities against Hemolysin A, while isotype-matched antibody did not display any neutralization activity against Hemolysin A. See Table 4.

TABLE 4 Neutralization of S. aureus Hemolysin A in THP-1 cytotoxicity assay IC₅₀ [M] for Hemolysin A AbPID neutralization H1H15375P 3.96E−09 H1H15376P 7.45E−09 H1H15377P 1.76E−09 H1H15378P 10.7E−09 H1H15379P 6.95E−09 H1H15380P 7.84E−09 H1H15381P 4.21E−09 H1H15399P 1.31E−09 H1H15404P 6.31E−09 H1H15405P 5.37E−09 H1H15408P 6.41E−09 H1H15410P 5.89E−09 H1H15414P 1.72E−09 H1H15418P2 2.47E−09 H1H15420P2 4.14E−09

Example 6. Neutralization of S. aureus Hemolysin A in Culture Supernatants Using a Rabbit RBC Hemolysis Assay

The Hemolysin A neutralization potency of purified mAbs using S. aureus culture supernatants was assessed using rabbit red blood cells (rRBCs). Culture supernatants were obtained by incubating S. aureus strains (American Type Culture Collection, Manassas, Va.) in TSB for 16 h at 37° C. (with shaking), removing the bacteria by centrifugation and filtering the toxin-containing medium. Titrations of purified antibody H1H15399P or isotype-matched control antibody (ranging from 10-0 μM with 1:2 serial dilutions in 1×PBS) were incubated with sterile filtered S. aureus culture supernatants (that would result in ≥80% cell lysis) in a 96 well plate for 30 minutes at 25° C. on a shaker. After the 30 minute incubation, 100 μl of the culture supernatant:mAb mixtures were added to 96 well round bottom plates containing 100 μl of 4% rRBCs (Colorado Serum Company, Denver, Colo.) in 1×PBS. Following a 1 h incubation at 37° C., plates were centrifuged for 5 min, 100 μl of the supernatant was removed gently to a new microtiter plate, and luminescence was read using a plate reader (SpectraMax i3x, Molecular Devices). All antibodies of the invention displayed similar neutralization activities against Hemolysin A, while isotype-matched antibody did not display any neutralization activity against Hemolysin A. See Table 5.

TABLE 5 Inhibition of native S. aureus Hemolysin A with anti-Hemolysin A mAb H1H15399 S. aureus IC₅₀ [M] for strain PFGE Hemolysin A Designation type binding GA201  USA100 6.697e−10 MRSA252  USA200 No inhibition* CA-127  USA300 2.339e−09 TCH1516  USA300 4.047e−09 MW2  USA400 No inhibition GA229  USA500 6.725e−10 00:50  USA600 No inhibition  8:03  USA700 7.091e−10 27-05  USA800 1.274e−09  94:1013 USA1000 5.434e−09 7031 USA1100 8.279e−10 *MRSA252 contains a stop codon in its Hemolysin A sequence resulting in no Hemolysin A protein secreted.

Example 7. Biacore Binding Affinities and Kinetic Constants of Human Anti-Hemolysin A Monoclonal Antibodies

Binding association and dissociation rate constants (k_(a) and k_(d), respectively), equilibrium dissociation constants and dissociation half-lives (K_(D) and t_(1/2), respectively) for wild type and mutant (Hla-H35L) Hemolysin A, binding to purified anti-Hemolysin A antibodies were determined using a real-time surface plasmon resonance biosensor assay on a Biacore T200 instrument. The Biacore sensor surface was derivatized with a monoclonal mouse anti-human Fc antibody (BR-1008-39, GE Healthcare) to capture approximately 150-360 RUs of anti-Hemolysin A monoclonal antibodies, expressed with a human Fc. Different concentrations of Hemolysin A toxins ranging from 100 nM to 1.56 nM were injected over the anti-Hemolysin A monoclonal antibody captured surface at a flow rate of 50 μL/min on Biacore T200. The binding of the Hemolysin A toxins to captured monoclonal antibodies, at 25° C. and 37° C., was monitored for 4 minutes and dissociation from the antibodies was monitored for 10 minutes with HBS-ET (0.01 M HEPES pH 7.4, 0.15 M NaCl, 3 mM EDTA, 0.05% v/v Surfactant P20) as the running buffer.

Kinetic association (k_(a)) and dissociation (k_(d)) rate constants were determined by processing and fitting the data to a 1:1 binding model using Scrubber 2.0c curve fitting software. Binding dissociation equilibrium constants (K_(D)) and dissociative half-lives (t_(1/2)) were then calculated from the kinetic rate constants as: K_(D) (M)=k_(d)/k_(a) and t_(1/2) (min)=[In2/(60*k_(d))].

Binding kinetics parameters for binding of wild type Hemolysin A and mutant Hemolysin A to different anti-Hemolysin A monoclonal antibodies at 25° C. and 37° C. are tabulated in Tables 6-9. As shown in Table 6, at 25° C., all the anti-Hemolysin A antibodies of the invention bound to wild type Hemolysin A with K_(D) values ranging from 171 pM to 26.2 nM. As shown in Table 7, at 37° C., all the anti-Hemolysin A antibodies of the invention bound to Hemolysin A with K_(D) values ranging from 260 pM to 76.3 nM. As shown in Table 8, at 25° C., all the anti-Hemolysin A antibodies of the invention bound to mutant Hemolysin A with K_(D) values ranging from 52.3 pM to 8.89 nM. As shown in Table 9, at 37° C., all the anti-Hemolysin A antibodies of the invention bound to mutant Hemolysin A with K_(D) values ranging from 74.7 pM to 18.7 nM.

TABLE 6 Binding Kinetics parameters of anti-Hemolysin A monoclonal antibodies binding to wild type Hemolysin A at 25° C. 25° C. k_(a) k_(d) K_(D) t_(1/2) Ab PID (l/mol * s) (1/s) [M] (min) H1H15420P2 7.67E+05 1.31E−04 1.71E−10 88 H1H15414P 3.62E+05 1.15E−04 3.18E−10 100 H1H15399P 3.59E+05 1.15E−04 3.22E−10 100 H1H15405P 7.76E+04 6.69E−05 8.62E−10 173 H1H15418P2 1.20E+05 1.02E−04 8.49E−10 113 H1H15377P 3.09E+05 3.15E−04 1.02E−09 37 H1H15380P 4.99E+05 4.43E−04 8.88E−10 26 H1H15375P 6.00E+04 1.27E−04 2.12E−09 91 H1H15381P 7.81E+05 1.50E−03 1.92E−09 8 H1H15404P 8.36E+04 3.37E−04 4.02E−09 34 H1H15408P 1.09E+05 8.32E−04 7.62E−09 14 H1H15410P 5.62E+04 4.62E−04 8.22E−09 25 H1H15376P 1.33E+05 2.18E−03 1.64E−08 5 H1H15378P 3.01E+05 7.88E−03 2.62E−08 1.5 H1H15379P 2.43E+05 6.34E−03 2.61E−08 1.8

TABLE 7 Binding Kinetics parameters of anti-Hemolysin A monoclonal antibodies binding to wild type Hemolysin A at 37° C. 37° C. k_(a) k_(d) K_(D) t_(1/2) Ab PID (l/mol * s) (1/s) [M] (min) H1H15420P2 1.18E+06 3.07E−04 2.60E−10 38 H1H15414P 5.57E+05 3.13E−04 5.62E−10 37 H1H15399P 4.90E+05 3.22E−04 6.57E−10 36 H1H15405P 1.17E+05 1.76E−04 1.51E−09 65 H1H15418P2 1.78E+05 3.50E−04 1.96E−09 33 H1H15377P 4.81E+05 1.08E−03 2.25E−09 11 H1H15380P 6.49E+05 1.48E−03 2.28E−09 8 H1H15375P 9.40E+04 4.28E−04 4.56E−09 27 H1H15381P 9.32E+05 6.50E−03 6.97E−09 1.8 H1H15404P 1.18E+05 2.07E−03 1.75E−08 6 H1H15408P 1.48E+05 4.05E−03 2.73E−08 2.9 H1H15410P 8.68E+04 2.51E−03 2.89E−08 5 H1H15376P 1.70E+05 8.42E−03 4.96E−08 1.4 H1H15378P 4.21E+05 2.29E−02 5.45E−08 0.5 H1H15379P 3.04E+05 2.32E−02 7.63E−08 0.5

TABLE 8 Binding kinetics parameters of anti-Hemolysin A monoclonal antibodies binding to mutant Hemolysin A at 25° C. 25° C. k_(a) k_(d) K_(D) t_(1/2) Ab PID (l/mol * s) (1/s) [M] (min) H1H15420P2 2.28E+06 1.19E−04 5.23E−11 97 H1H15414P NB NB NB NB H1H15399P 9.98E+05 1.00E−04 1.00E−10 116 H1H15405P 2.46E+05 5.82E−05 2.37E−10 199 H1H15418P2 3.96E+05 7.43E−05 1.88E−10 155 H1H15377P 1.12E+06 4.11E−04 3.67E−10 28 H1H15380P 1.39E+06 3.87E−04 2.79E−10 30 H1H15375P 1.76E+05 1.17E−04 6.65E−10 99 H1H15381P 2.26E+06 1.22E−03 5.40E−10 9 H1H15404P 2.68E+05 2.94E−04 1.10E−09 39 H1H15408P 3.47E+05 7.05E−04 2.03E−09 16 H1H15410P 1.52E+05 3.99E−04 2.63E−09 29 H1H15376P 4.22E+05 1.45E−03 3.43E−09 8 H1H15378P 7.66E+05 6.81E−03 8.89E−09 1.7 H1H15379P 6.81E+05 4.43E−03 6.51E−09 2.6 *NB indicates that under the experimental conditions, Hemolysin A toxin did not bind to the captured anti-Hemolysin A monoclonal antibody.

TABLE 9 Binding Kinetics parameters of anti-Hemolysin A monoclonal antibodies binding to mutant Hemolysin A at 37° C. 37° C. k_(a) k_(d) K_(D) t_(1/2) Ab PID (l/mol * s) (1/s) [M] (min) H1H15420P2 3.56E+06 2.66E−04 7.47E−11 43 H1H15414P NB NB NB NB H1H15399P 1.42E+06 2.78E−04 1.96E−10 42 H1H15405P 4.30E+05 1.52E−04 3.54E−10 76 H1H15418P2 5.68E+05 2.29E−04 4.03E−10 51 H1H15377P 1.59E+06 1.37E−03 8.64E−10 8 H1H15380P 1.88E+06 1.31E−03 6.95E−10 9 H1H15375P 3.11E+05 3.70E−04 1.19E−09 31 H1H15381P 2.45E+06 4.66E−03 1.90E−09 2.5 H1H15404P 3.35E+05 1.81E−03 5.41E−09 6 H1H15408P 4.38E+05 2.93E−03 6.68E−09 4 H1H15410P 2.26E+05 2.19E−03 9.72E−09 5 H1H15376P 4.73E+05 4.41E−03 9.32E−09 2.6 H1H15378P 9.43E+05 1.68E−02 1.78E−08 0.7 H1H15379P 6.41E+05 1.20E−02 1.87E−08 1 *NB indicates that under the experimental conditions, Hemolysin A toxin did not bind to the captured anti-Hemolysin A monoclonal antibody.

Example 8. Mechanism of Anti-Hemolysin A mAb Blocking Activity

To determine if Hemolysin A mAbs exert their function by blocking the interaction of the toxin with its specific receptor, ADAM10, host cell-associated metalloprotease activity was measured using a fluorogenic peptide substrate assay using A549 cells incubated with Hemolysin A. Titrations of Hemolysin A mAbs (H1H15377P, H1H15381P and H1H15399P) were pre-incubated with 3 nM purified Hemolysin A for 15 min at 37° C. prior to addition to 96 well plates containing 2.5×10⁴ A549 cells in Ham's F-12K (supplemented with 10% heat-inactivated FBS and L-glutamine). After incubation for 60 min at 37° C., 5 μM fluorogenic peptide substrate (Mca-PLAVQ-Dpa-RSSSR-NH2, R&D Systems, Minneapolis, Minn.) was added, incubated for 15 min at 37° C. and fluorescence intensity was read using a plate reader (excitation filter of 320 nm and an emission filter of 405 nm, SpectraMax i3x, Molecular Devices) and expressed as relative fluorescence units. Antibodies of the invention blocked the toxin-induced increase in ADAM10 activity, while isotype-matched antibody did not display any effect on the toxin-induced increased ADAM10 activity (FIG. 4 a ). This suggested that antibodies of the invention blocked interaction of Hemolysin A to its receptor.

To further demonstrate that the Hemolysin A mAbs prevented binding of the toxin to the host cell membrane, membrane binding experiments were performed in the presence of the Hemolysin A mAbs using rabbit RBCs (rRBCs), and the association of the toxin with the rRBC membrane was detected by Western blot analysis. To avoid lysis of the rRBCs, binding experiments were performed at 4° C. Titrations of Hemolysin A mAbs (H1H15377P and H1H15399P) were pre-incubated with 10 nM Hemolysin A for 15 min at 37° C. prior to addition to washed rRBCs (10% in 250 μl PBS) and incubated for 60 min at 4° C. rRBCs were pelleted, supernatant removed and cells were lysed by three cycles of resuspension in 1 ml of ddH₂O, incubation for 10 min at 25° C. and centrifugation at 16,100×g Membranes were solubilized in 10 mM Tris-HCl, pH 7.4, 150 mM NaCl, 1% Triton X-100 and 1% sodium deoxycholate. Solubilized samples were reduced, boiled, and separated on a 4-12% SDS-PAGE gel (Invitrogen, Carlsbad, Calif.) transferred to PVDF membrane (Invitrogen, Carlsbad, Calif.) and Hemolysin A monomer was detected with a pAb (IBT BioServices, Rockville, Md.). Antibodies of the invention prevented binding of Hemolysin A to rRBC membrane while isotype-matched antibody did not display any effect (FIG. 4 b ).

Example 9. In Vivo Efficacy of Human Anti-Hemolysin A mAbs Administered Prophylactically in a Dermonecrosis Mouse Model

In order to determine if anti-Hemolysin A mAbs of the invention were able to decrease or prevent S. aureus-induced skin lesions, purified antibodies were tested prophylactically in an in vivo dermonecrosis model using female BALB/c mice (n=3-5) (Bubeck Wardenburg et al., (2008) J. Infect. Dis. 198:1166-1170). Two days prior to infection, fur was removed from the abdominal area by shaving and applying hair removal lotion. One day prior to infection, mice were injected i.p. on the left side of the abdomen with a single dose of either 5 mg/kg or 0.5 mg/kg of each individual antibody: H1H15375P, H1H15376P, H1H15377P, H1H15378P, H1H15379P, H1H15380P, H1H15381P, H1H15399P, H1H15404P, H1H15405P, H1H15408P, H1H15410P, H1H15414P, H1H15418P2, H1H15420P2, or an isotype-matched control antibody. On the day of infection, mice were challenged subcutaneously, on the right side of the abdomen, with 50 μls of S, aureus CA-127 (˜1-2×10⁸ CFU/mouse) that had been grown to log phase (OD₆₀₀≤1) in TSB at 37° C., washed and suspended in PBS. Mouse lesions were measured with a digital caliper on day 2 post-infection.

All antibodies of the invention were efficacious at both tested doses. When administered at 5 mg/kg, all antibodies, showed similar efficacy, reducing dermonecrotic lesions 80-90% when compared to isotype-matched control antibody (Table 10). Similarly, when administered to animals at 0.5 mg/kg, all antibodies of the invention (with the exception of H1H15410P), showed reductions in lesion size when compared to those treated with the isotype-matched antibody (Table 10). Reduction in lesion size, however, ranged from 40-80%, with H1H15410P showing no effect at this dose. Antibodies H1H15380P, H1H15381P, H1H15405P and H1H15414P were the most efficacious when administered at 0.5 mg/kg, with >80% reduction in lesion sizes. Comparison of the 5 mg/kg and 0.5 mg/kg groups showed a dose-dependent effect: mice receiving antibodies at the 5 mg/kg dose had smaller lesions compared to mice receiving the same antibody at the 0.5 mg/kg dose.

TABLE 10 Lesion size comparison for anti-Hemolysin A monoclonal antibodies in a prophylaxis murine dermonecrosis model, Day 2 post-infection Mice receiving 5 mg/kg mAb and Mice receiving 0.5 mg/kg mAb and infected with 1.3 × 10⁸ CFU infected with 1.5 × 10⁸ CFU S. aureus CA-127 S. aureus CA-127 Decrease Mean Decrease Mean Relative Lesion Relative Lesion Mice to Isotype Size Mice to Isotype Size AbPID (n) (%) (mm) SD (n) (%) (mm) SD H1H15375P 5 90.7 31.6 6.3 5 68.0 63.2 29.2 H1H15376P 5 89.2 37.0 7.2 5 79.9 39.8 9.4 H1H15377P 5 85.7 48.8 7.0 5 57.5 84.1 70.1 H1H15378P 5 88.4 39.5 9.9 5 67.1 65.0 30.4 H1H15379P 5 88.5 39.1 13.3 5 76.9 45.6 39.9 H1H15380P 5 87.1 44.2 8.0 5 82.1 35.4 23.5 H1H15381P 5 83.9 55.1 22.2 5 85.1 29.5 26.0 H1H15399P 5 89.0 37.7 13.4 5 69.9 59.6 18.3 H1H15404P 5 86.7 45.5 12.5 5 46.6 105.7 40.5 H1H15405P 5 92.1 27.0 7.1 5 86.4 26.9 11.1 H1H15408P 5 90.1 33.9 10.4 5 73.1 53.3 17.2 H1H15410P 5 86.5 46.2 9.8 4 0.0 216.8 98.1 H1H15414P 5 90.2 33.5 17.5 5 82.1 35.5 12.5 H1H15418P2 5 86.6 45.8 6.7 5 48.9 101.1 63.1 H1H15420P2 5 85.8 48.5 7.9 5 62.2 74.7 37.5 Isotype control 3 0.0 341.6 38.6 5 0.0 197.8 56.8

To further interrogate the ability of the anti-Hemolysin A mAbs to decrease lesion size, the mAbs were administered prophylactically at three different doses and compared to two other anti-Hemolysin A mAbs, LTM14 (See e.g., U.S. Pat. No. 8,715,673—SEQ ID NOs: 1 and 2; or Foletti et al., Mechanism of Action and In Vivo Efficacy of a Human-Derived Antibody against Staphylococcus α-Hemolysin, J. Mol. Biol. 425: 1641-1654 (2013)) and LC10 (see e.g., WO2012/109285-SEQ ID NOs: 57 and 58). Fur was removed from female BALB/c mice as described above two days prior to infection. One day prior to infection, mice (n=5 per group) were injected i.p. on the left side of the abdomen with a single dose of 5 mg/kg, 0.5 mg/kg or 0.125 mg/kg of each individual antibody: H1H15377P, H1H15381P, H1H15399P, LTM14, LC10 or an isotype-matched control antibody. On the day of infection, mice were challenged subcutaneously, on the right side of the abdomen, with 50 μls of S. aureus CA-127 (MRSA strain; 2.5×10⁸ CFU/mouse) or S. aureus Newman (MSSA strain; 2.5×10⁸ CFU/mouse) that had been grown to log phase (OD₆₀₀≤1) in TSB at 37° C., washed and suspended in PBS. Mouse lesions were measured with a digital caliper on day 2 post-infection.

All antibodies of the invention were efficacious at all three tested doses using both MRSA and MSSA S. aureus strains. When administered at 5 mg/kg, all antibodies, including LC10 and LTM14, showed similar efficacy against both S. aureus CA-127 (FIG. 5 a ) and Newman (FIG. 6 a ), reducing lesions ≥85% when compared to isotype-matched control antibody. Similarly, when administered to mice at 0.5 mg/kg, all antibodies showed similar reductions of 50-60% in lesion size when compared to those treated with the isotype-matched antibody (FIGS. 5 b and 6 b ). Reductions in lesion size, however, were greater with H1H15377P and H1H15399P compared to H1H15381P, LC10 and LTM14 when administered at 0.125 mg/kg using both S. aureus CA-127 (FIG. 5 c ) and Newman (FIG. 6 c ) ranging from 30-40%, compared to those treated with the isotype-matched antibody. For all antibodies, comparison of the 5 mg/kg, 0.5 mg/kg and 0.125 mg/kg groups showed a dose-dependent effect: mice receiving antibodies at the higher concentrations had the smaller lesions (5 mg/kg dose lesions <0.5 mg/kg dose lesions <0.125 mg/kg dose lesions).

Example 10. Bacteria Counts in Skin of Mice Administered Anti-Hemolysin A mAbs Prophylactically

Three purified antibodies of the invention, H1H15377P, H1H15381P and H1H15399P, were tested in a dermonecrosis model to determine if there were any observed changes in the bacterial burden in the skin of mice prophylactically treated with the antibodies. The antibodies of the invention were also compared to two other anti-Hemolysin A mAbs, LC10 and LTM14. Two days prior to infection, fur was removed from the abdominal area of female BALB/c mice by shaving and applying hair removal lotion. One day prior to infection, mice were injected i.p. on the left side of the abdomen with a single dose of 5 mg/kg of each individual antibody: H1H15377P, H1H15381P and H1H15399P, LTM14, LC10 or an isotype-matched control antibody. On the day of infection, mice (n=5 per group) were challenged, subcutaneously, on the right side of the abdomen, with 50 μls of S. aureus CA-127 (MRSA strain; 2.5×10⁸ CFU/mouse) or Newman (MSSA strain; 2.9×10⁸ CFU/mouse) that had been grown to log phase (OD₆₀₀≤1) in TSB at 37° C., washed and suspended in PBS. The mice were euthanized by anesthesia 2 days post-infection, the lesion area (and surrounding skin) was excised using an 8-mm dermal biopsy punch and homogenized. Serial dilutions of the skin lysates were plated on TSA plates. Plates were incubated overnight (16-18 hours) at 37° C. and bacterial colonies were counted the next day for determination of bacterial burden.

Antibodies H1H15377P and H1H15399P reduced the bacterial burden in the skin of mice infected with both S. aureus CA-127 (FIG. 7 a ) and Newman (FIG. 7 b ); specifically, 5 mg/kg of either antibody resulted in a 1-1.5 log reduction in skin bacterial burden, compared to the levels of bacterial burden determined for the animals treated with the isotype-matched control antibody. The same dose of H1H15381P, LTM14 or LC10 resulted in 0-0.5 log reduction in skin bacterial burden. The results indicate that H1H15377P and H1H15399P were most effective in reducing bacterial burden in the skin of infected mice.

Example 11. In Vivo Efficacy of Anti-Hemolysin A mAbs Administered Therapeutically

In order to determine if mAbs in the invention can also decrease lesion size if administered after infection, purified antibodies were tested therapeutically in an in vivo dermonecrosis model using female BALB/c mice (n=5). Two days prior to infection, fur was removed from the abdominal area by shaving and applying hair removal lotion. On the day of infection, mice were challenged subcutaneously, on the right side of the abdomen, with 50 μls of S. aureus CA-127 (˜1-2×10⁸ CFU/mouse) that had been grown to log phase (OD₆₀₀≤1) in TSB at 37° C., washed and resuspended in PBS. Two hours after infection, mice were injected i.p. on the left side of the abdomen with a single dose of 0.5 mg/kg of each individual antibody: H1H15375P, H1H15376P, H1H15377P, H1H15378P, H1H15379P, H1H15380P, H1H15381P, H1H15399P, H1H15404P, H1H15405P, H1H15408P, H1H15410P, H1H15414P, H1H15418P2, H1H15420P2 or an isotype-matched control antibody. Mouse lesions were measured with a digital caliper on day 2 post-infection.

All antibodies of the invention were efficacious in reducing lesion size when administered to animals at 0.5 mg/kg two hours after infection (Table 11). Reductions in dermonecrotic lesion sizes ranged from 50-83%. Eight of the antibodies (H1H15376P, H1H15377P, H1H15378P, H1H15379P, H1H15380P, H1H15399P, H1H15418P2 and H1H15420P2) showed >70% reduction in lesions sizes.

TABLE 11 Lesion size comparison for anti-Hemolysin A monoclonal antibodies in a therapeutic murine dermonecrosis model, Day 2 post-infection Mice receiving 0.5 mg/kg mAb and infected with 1.1 × 10⁸ CFU S. aureus CA-127 Decrease Mean Relative to Lesion Mice Isotype Size AbPID (n) (%) (mm) SD H1H15375P 5 69.2 52.8 44.9 H1H15376P 5 79.4 35.4 11.4 H1H15377P 5 73.1 46.2 35.0 H1H15378P 5 82.8 29.6  8.3 H1H15379P 5 74.5 43.8 19.4 H1H15380P 5 79.5 35.2 15.8 H1H15381P 5 59.0 70.5 53.2 H1H15399P 4 73.2 46.1 15.4 H1H15404P 5 56.2 75.3 24.4 H1H15405P 5 69.8 51.9 19.1 H1H15408P 5 63.9 62.1 21.3 H1H15410P 5 50.2 85.5 38.1 H1H15414P 5 80.9 32.8 12.9 H1H15418P2 5 70.6 50.4 11.2 H1H15420P2 5 73.7 45.2 30.1 Isotype 5  0.0 171.8 97.9 control

Example 12. In Vivo Efficacy of Anti-Hemolysin A mAbs in an Acute Pneumonia Model Using a Methicillin-Sensitive Staphylococcus aureus (MSSA) Strain

Survival of mice administered antibodies at 5 mg/kg prophylactically. In order to determine the efficacy of the mAbs against a MSSA strain when administered prophylactically, the following antibodies H1H15375P, H1H15376P, H1H15377P, H1H15378P, H1H15379P, H1H15380P, H1H15381P, H1H15399P and H1H15414P were selected for study in an acute pneumonia model using S. aureus Newman (modified from Bubeck Wardenburg et al., (2007) Infect. Immun. 75:1040-1044). Female C57BL/6 mice (n=5) were injected i.p. with a single dose of 5 mg/kg of H1H15375P, H1H15376P, H1H15377P, H1H15378P, H1H15379P, H1H15380P, H1H15381P, H1H15399P, H1H15414P or an isotype-matched control antibody. One day post-injection of the mAbs, mice were challenged intra-tracheally with 50 μls of S. aureus Newman (1.7×10⁸ CFU/mouse) that had been grown to log phase (OD₆₀₀≤1) in TSB at 37° C., washed and resuspended in PBS. The mice were monitored for survival for a total of six days post-infection.

As seen in Table 12, administration of antibody H1H15375P, H1H15376P, H1H15378P, H1H15379P, H1H15380P, H1H15381P, H1H15399P or H1H15414P resulted in 100% survival. Administration of H1H15377P resulted in 80% survival to day 6. All antibodies of the invention increased survival of mice infected with a S. aureus MSSA strain when given prophylactically at 5 mg/kg in an acute pneumonia model of infection.

TABLE 12 Survival of mice administered 5 mg/kg anti-Hemolysin A monoclonal antibodies prophylactically in an acute pneumonia model using an MSSA strain S. aureus Newman (MSSA) mAb dose: 5 mg/kg Mice Survival at D6 post-infection AbPID (n) (%) H1H15375P 5 100 H1H15376P 5 100 H1H15377P 5 80 H1H15378P 5 100 H1H15379P 5 100 H1H15380P 5 100 H1H15381P 5 100 H1H15399P 5 100 H1H15414P 5 100 Isotype control 5 20

Survival of mice administered antibodies at 2.5 mg/kg prophylactically. To determine if the antibodies would also be effective at a lower dose in the acute pneumonia model against a MSSA strain, C57BL/6 female mice (n=5), were injected i.p. with a single dose of 2.5 mg/kg of H1H15375P, H1H15377P, H1H15378P, H1H15379P, H1H15380P, H1H15381P, H1H15399P, H1H15414P, or an isotype-matched antibody. One day post-injection of the mAbs, mice were challenged intra-tracheally with 50 μls of S. aureus Newman (7.5×10⁷ CFU/mouse) that had been grown to log phase (OD₆₀₀≤1) in TSB at 37° C., washed and resuspended in PBS. The mice were monitored for survival for a total of six days post-infection.

As seen in Table 12, administration of antibody H1H15376P, H1H15377P, H1H15379P, H1H15381P, H1H15399P or H1H15414P resulted in 100% survival to day 6, whereas, administration of antibody H1H15378P or H1H15380P resulted in 80% survival. Antibody H1H15375P was less efficacious when compared to the other antibodies, providing only 60% protection (Table 13).

The results indicate that antibodies H1H15375P, H1H15376P, H1H15378P, H1H15379P, H1H15380P, H1H15381P, H1H15399P, H1H15414P and H1H15377P are efficacious in reducing cytotoxic effects of Hemolysin A and increasing survival in a murine acute pneumonia model using S. aureus MSSA strain even when the mAbs are administered at a lower dose.

TABLE 13 Survival of mice administered 2.5 mg/kg anti-Hemolysin A monoclonal antibodies prophylactically in an acute pneumonia model using an MSSA strain S. aureus Newman (MSSA) mAb dose: 2.5 mg/kg Survival at D6 Mice post-infection AbPID (n) (%) H1H15375P 5 60 H1H15376P 5 100 H1H15377P 5 100 H1H15378P 5 80 H1H15379P 5 100 H1H15380P 5 80 H1H15381P 5 100 H1H15399P 5 100 H1H15414P 5 100 Isotype control 5 0

Example 13. In Vivo Efficacy of Anti-Hemolysin A mAbs in an Acute Pneumonia Model Using a Methicillin-Resistant Staphylococcus aureus (MRSA) Strain

Survival of mice administered antibodies at 5 mg/kg prophylactically. In order to test the efficacy of the mAbs against a MRSA strain, the following antibodies H1H15375P, H1H15376P, H1H15377P, H1H15378P, H1H15379P, H1H15380P, H1H15381P, H1H15399P and H1H15414P were selected for study in a prophylactic acute pneumonia model using S. aureus CA-127. Female C57BL/6 mice (n=5) were injected i.p. with a single dose of 5 mg/kg of H1H15375P, H1H15376P, H1H15377P, H1H15378P, H1H15379P, H1H15380P, H1H15381P, H1H15399P, H1H15414P, or an isotype-matched control antibody. One day post-injection of the mAbs, mice were challenged intra-tracheally with 50 μls containing either 2.2×10⁸ CFU (low inoculum) or 4.8×10⁸ CFU (high inoculum) of S. aureus CA-127 that had been grown to log phase (OD₆₀₀≤1) in TSB at 37° C., washed and resuspended in PBS. The mice were monitored for survival for a total of six days post-infection.

Eight of the nine invention antibodies showed efficacy when mice were challenged with the low inoculum. Specifically, antibodies H1H15375P, H1H15377P, H1H15378P, H1H15379P, H1H15380P, H1H15381P and H1H15399P were equally efficacious, resulting in 100% survival to day 6 (Table 14). Administration of antibody H1H15414P resulted in 80% survival. H1H15376P demonstrated no protection, as mice receiving this antibody did not survive to day 6. None of the animals treated with the isotype-matched antibody survived to day 6 (Table 13)

At a higher inoculum, greater differentiation in efficacy between the invention antibodies was observed. As seen in Table 13, antibodies H1H15377P and H1H15399P were the most efficacious of the antibodies tested, resulting in 100% survival to day 6. Administration of antibodies H1H15414P, H1H15378P, H1H15379P and H1H15381P resulted in 60% survival to day 6, whereas none of the animals in the group treated with the isotype-matched control antibody survived to day 6. Antibodies H1H15375P, H1H15376P and H1H15380P had lower efficacy than the other invention antibodies tested, resulting in 20%, 0% or 40% survival to day 6, respectively (Table 13).

The results indicate that H1H15375P, H1H15377P, H1H15378P, H1H15379P, H1H15380P, H1H15381P, H1H15399P and H1H15414P are efficacious at reducing the cytotoxic effects of Hemolysin A and increasing survival when given prophylactically at 5 mg/kg in an acute pneumonia model of infection with a lower inoculum of a S. aureus MRSA strain. Two antibodies, H1H15377P and H1H15399P were also 100% efficacious when a higher inoculum of a S. aureus MRSA strain was used in this model.

TABLE 14 Survival of mice administered 5 mg/kg anti-Hemolysin A monoclonal antibodies prophylactically in an acute pneumonia model using a MRSA strain S. aureus CA-127 Low Inoculum High Inoculum (MRSA) (2.2 × 10⁸ (4.8 × 10⁸ mAb dose: 5 mg/kg CFU) CFU) Mice Survival Survival AbPID (n) (%) (%) H1H15375P 5 100 20 H1H15376P 5 0 0 H1H15377P 5 100 100 H1H15378P 5 100 60 H1H15379P 5 100 60 H1H15380P 5 100 40 H1H15381P 5 100 60 H1H15399P 5 100 100 H1H15414P 5 80 60 Isotype 5 0 0 control

Survival of mice administered antibodies at 2.5 mg/kg prophylactically. To determine if the antibodies would also be effective at a lower dose in the acute pneumonia model against a MRSA strain, female C57BL/6 mice (n=5) were injected i.p. with a single dose of 2.5 mg/kg of H1H15375P, H1H15376P, H1H15377P, H1H15378P, H1H15379P, H1H15380P, H1H15381P, H1H15399P, H1H15414P, or an isotype-matched control antibody. One day post-injection of the mAbs, mice were challenged intra-tracheally with 50 μls of S. aureus CA-127 (3.0×10⁸ CFU/mouse) that had been grown to log phase (OD₆₀₀≤1) in TSB at 37° C., washed and resuspended in PBS. The mice were monitored for survival for a total of six days post-infection.

All invention antibodies tested (H1H15375P, H1H15377P, H1H15378P, H1H15379P, H1H15380P, H1H15381P, H1H15399P or H1H15414P) were equally efficacious, resulting in 100% survival to day 6, whereas none of the animals in the group treated with the isotype-matched control antibody survived until day 6 (Table 15). The results indicate that H1H15375P, H1H15377P, H1H15378P, H1H15379P, H1H15380P, H1H15381P, H1H15399P and H1H15414P are efficacious at reducing the cytotoxic effects of Hemolysin A and increasing survival when given prophylactically at 2.5 mg/kg in an acute pneumonia model of infection with a S. aureus MRSA strain.

TABLE 15 Survival of mice administered 2.5 mg/kg anti-Hemolysin A monoclonal antibodies prophylactically in an acute pneumonia model using MRSA strain S. aureus CA-127 (MRSA) mAb dose: 2.5 mg/kg Mice Survival at D6 post-infection AbPID (n) (%) H1H15375P 5 100 H1H15377P 5 100 H1H15378P 5 100 H1H15379P 5 100 H1H15380P 5 100 H1H15381P 5 100 H1H15399P 5 100 H1H15414P 5 100 Isotype control 5  0

Bacteria counts in lungs of mice administered H1H15399P and H1H15376P prophylactically. Two purified antibodies of the invention, H1H15399P and H1H15376P, were tested in an acute pneumonia study to determine if there were any observed changes in the bacterial burden in the lungs of mice prophylactically treated with the antibodies. Groups of female C57BL/6 mice (n=5) were injected i.p. with one of three doses of H1H15399P, a single dose of H1H15376P, or an isotype-matched control antibody (5 mg/kg). One day post-injection, mice were challenged intra-tracheally with 50 μls of S. aureus CA-127 (1.6×10⁸ CFU/mouse) that had been grown to log phase (OD₆₀₀≤1) in TSB at 37° C., washed and resuspended in PBS. The mice were euthanized by anesthesia 18 hours post-infection and lungs were extracted and homogenized. Serial dilutions of the lung lysates were plated on TSA plates. Plates were incubated overnight (16-18 hours) at 37° C. and bacterial colonies were counted the next day for determination of bacterial burden.

Antibody H1H15399P reduced the bacterial burden in lungs of infected mice (Table 16); specifically, all three doses of H1H15399P tested resulted in a 1 to 1.5 log reduction in lung bacterial burden, compared to the levels of bacterial burden determined for the animals treated with the isotype-matched control antibody. In addition, this decrease in lung bacterial burden was dose-dependent. Antibody H1H15376P did not display any efficacy in this model, showing lung bacterial lung burden similar to the isotype-matched antibody. The results indicate that H1H15399P was able to reduce bacterial burden in the lungs of infected mice.

TABLE 16 Bacterial counts in lungs of mice administered anti-Hemolysin A monoclonal antibodies H1H15399P and H1H15376P prophylactically in an acute pneumonia model using a MRSA strain Organ Burden Mice Dose mean AbPID (n) (mg/kg) CFU/lung SD H1H15399P 5 5 5.50E+06 2.30E+06 5 2.5 1.11E+07 1.10E+07 5 1.25 1.04E+07 7.06E+06 H1H15376P 5 5 1.47E+08 2.33E+08 Isotype 4 5 2.45E+08 1.72E+08 control

To further interrogate the ability of the anti-Hemolysin A mAbs to reduce bacterial burden in the lungs, three mAbs (H1H15377P, H1H15381P, H1H15399P) that had demonstrated increased survival were administered prophylactically at two different doses and compared to two other anti-Hemolysin A mAbs, LC10 and LTM14. Groups of female C57BL/6 mice (n=5) were injected i.p. with a single dose of 1.25 mg/kg or 0.325 mg/kg of each individual antibody: H1H15377P, H1H15381P, H1H15399P, LTM14, LC10 or an isotype-matched control antibody. One day post-injection, mice were challenged intra-tracheally with 50 μls of S. aureus CA-127 (1.3×10⁸ CFU/mouse) that had been grown to log phase (OD₆₀₀≤1) in TSB at 37° C., washed and resuspended in PBS. The mice were euthanized by anesthesia 18 hours post-infection and lungs were extracted and homogenized. Serial dilutions of the lung lysates were plated on TSA plates. Plates were incubated overnight (16-18 hours) at 37° C. and bacterial colonies were counted the next day for determination of bacterial burden.

All three antibodies of the invention tested were efficacious when administered at 1.25 mg/kg compared to LTM14, LC10 and isotype-matched control antibody, decreasing bacterial burden in the lungs by 1 log (FIG. 8 a ). H1H15399P was also effective at decreasing bacterial burden when administered at 0.325 mg/kg (FIG. 8 b ). All other Hemolysin A mAbs tested did not significantly reduce bacteria in the lungs of the mice at this lower dose (FIG. 8 b ).

Example 14. Octet Cross-Competition Between Different Anti-Hemolysin A Monoclonal Antibodies Using Pre-Complex Method

To assess whether two antibodies compete with one another for binding epitopes on Hemolysin A (purified from Staphylococcus aureus), binding competition between anti-Hemolysin A monoclonal antibodies was determined using a real time, label-free bio-layer interferometry assay on an Octet RED384 biosensor (Pall ForteBio Corp.). The entire experiment was performed at 25° C. in 0.01M HEPES pH7.4, 0.15M NaCl, 3 mM EDTA, 0.05% v/v Tween-20, 1.0 mg/mL BSA (Octet HBS-ET buffer) with the plate shaking at the speed of 1000 rpm. About 1.5-2.5 nm of anti-Hemolysin A monoclonal antibody was first captured onto anti-hFc antibody coated Octet biosensor tips (Pall ForteBio Corp., #18-5060) by submerging the tips for two minutes into wells containing a 50 μg/mL solution of anti-Hemolysin monoclonal antibody (mAb-1). The antibody captured biosensor tips were then saturated with a blocking H4H isotype control monoclonal antibody (blocking mAb) by dipping into wells containing 100 μg/mL solution of blocking rnAb for three minutes. The biosensor tips were then subsequently dipped for four minutes into wells, containing 100 nM Hemolysin A previously incubated for 2 hours with 1 μM of a second anti-Hemolysin A monoclonal antibody (rnAb-2). The biosensor tips were washed in Octet HBS-ET buffer in between every step of the experiment. The real-time binding response was monitored during the course of the experiment and the binding response at the end of every step was recorded. The response of Hemolysin A pre-complexed mAb-2 binding to mAb-1 was corrected for background binding, compared and competitive/non-competitive behavior of different anti-Hemolysin A monoclonal antibodies was determined. Table 17 explicitly defines the relationships of antibodies competing in both directions, independent of the order of binding.

TABLE 17 Cross-competition of anti-Hemolysin A antibodies for binding to Hemolysin A First mAb (mAb-1) Captured using AHC mAb-2 Antibodies Shown to Octet Biosensors Compete with mAb-1 H1H15404P H1H15410P, H1H15376P, H1H15418P2 H1H15410P H1H15404P, H1H15376P, H1H15418P2 H1H15376P H1H15404P, H1H15410P, H1H15418P2, H1H15375P, H1H15377P, H1H15405P H1H15418P2 H1H15404P, H1H15410P, H1H15376P, H1H15375P, H1H15377P, H1H15405P H1H15375P H1H15376P, H1H15418P2, H1H15377P, H1H15405P, H1H15379P, H1H15408P, H1H15381P, H1H15378P, H1H15399P H1H15377P H1H15376P, H1H15418P2, H1H15375P, H1H15405P, H1H15379P, H1H15408P, H1H15381P, H1H15378P, H1H15399P H1H15405P H1H15376P, H1H15418P2, H1H15375P, H1H15377P, H1H15379P, H1H15408P, H1H15381P, H1H15378P, H1H15399P H1H15379P H1H15375P, H1H15377P, H1H15405P, H1H15408P, H1H15381P, H1H15378P, H1H15399P, H1H15420P2, H1H15380P, H1H15414P H1H15408P H1H15375P, H1H15377P, H1H15405P, H1H15379P, H1H15381P, H1H15378P, H1H15399P, H1H15420P2, H1H15380P, H1H15414P H1H15381P H1H15375P, H1H15377P, H1H15405P, H1H15379P, H1H15408P, H1H15378P, H1H15399P, H1H15420P2, H1H15380P, H1H15414P H1H15378P H1H15375P, H1H15377P, H1H15405P, H1H15379P, H1H15408P, H1H15381P, H1H15399P, H1H15420P2, H1H15380P, H1H15414P H1H15399P H1H15375P, H1H15377P, H1H15405P, H1H15379P, H1H15408P, H1H15381P, H1H15378P, H1H15420P2, H1H15380P, H1H15414P H1H15420P2 H1H15379P, H1H15408P, H1H15381P, H1H15378P, H1H15399P, H1H15380P, H1H15414P H1H15380P H1H15379P, H1H15408P, H1H15381P, H1H15378P, H1H15399P, H1H15420P2 H1H15414P H1H15379P, H1H15408P, H1H15381P, H1H15378P, H1H15399P, H1H15420P2

The present invention is not to be limited in scope by the specific embodiments described herein. Indeed, various modifications of the invention in addition to those described herein will become apparent to those skilled in the art from the foregoing description and the accompanying figures. Such modifications are intended to fall within the scope of the appended claims. 

What is claimed is:
 1. A polynucleotide encoding a heavy chain variable region (HCVR) of an antibody or antigen-binding fragment thereof that binds to Hemolysin A, wherein the HCVR comprises three heavy chain complementarity determining regions (CDRs) (HCDR1, HCDR2, and HCDR3), wherein the HCDR1 comprises the amino acid sequence set forth in SEQ ID NO: 144, the HCDR2 comprises the amino acid sequence set forth in SEQ ID NO: 146, and the HCDR3 comprises the amino acid sequence set forth in SEQ ID NO:
 148. 2. The polynucleotide of claim 1, wherein the HCVR comprises the amino acid sequence set forth in SEQ ID NO:
 142. 3. The polynucleotide of claim 1, wherein the polynucleotide comprises the HCDR1 nucleic acid sequence set forth in SEQ ID NO: 143; the HCDR2 nucleic acid sequence set forth in SEQ ID NO: 145; and the HCDR3 nucleic acid sequence set forth in SEQ ID NO:
 147. 4. The polynucleotide of claim 1, wherein the polynucleotide comprises the HCVR nucleic acid sequence set forth in SEQ ID NO:
 141. 5. The polynucleotide of claim 1, wherein the antibody further comprises an immunoglobulin constant region.
 6. The polynucleotide of claim 5, wherein the immunoglobulin constant region is an IgG1 constant region.
 7. The polynucleotide of claim 1, wherein the antibody comprises the heavy chain amino acid sequence set forth in SEQ ID NO:
 158. 8. The polynucleotide of claim 1, wherein the polynucleotide comprises the heavy chain nucleic acid sequence set forth in SEQ ID NO:
 157. 9. A vector comprising the polynucleotide of claim
 1. 10. A polynucleotide encoding a light chain variable region (LCVR) of an antibody or antigen-binding fragment thereof that binds to Hemolysin A, wherein the LCVR comprises three light chain complementarity determining regions (CDRs) (LCDR1, LCDR2, and LCDR3), wherein the LCDR1 comprises the amino acid sequence set forth in SEQ ID NO: 152, the LCDR2 comprises the amino acid sequence set forth in SEQ ID NO: 154, and the LCDR3 comprises the amino acid sequence set forth in SEQ ID NO:
 156. 11. The polynucleotide of claim 10, wherein the LCVR comprises the amino acid sequence of SEQ ID NO:
 150. 12. The polynucleotide of claim 10, wherein the polynucleotide comprises the LCDR1 nucleic acid sequence set forth in SEQ ID NO: 151; the LCDR2 nucleic acid sequence set forth in SEQ ID NO: 153; and the LCDR3 nucleic acid sequence set forth in SEQ ID NO:
 155. 13. The polynucleotide of claim 10, wherein the polynucleotide comprises the LCVR nucleic acid sequence set forth in SEQ ID NO:
 149. 14. The polynucleotide of claim 10, wherein the antibody comprises the light chain amino acid sequence set forth in SEQ ID NO:
 160. 15. The polynucleotide of claim 10, wherein the polynucleotide comprises the light chain nucleic acid sequence set forth in SEQ ID NO:
 159. 16. A vector comprising the polynucleotide of claim
 10. 